How to Cite a Secondary Source in APA, MLA & Chicago Format (2026 Guide)

You found the perfect quote for your research paper, but there's a catch — it's cited in another source, and you can't find the original. Sound familiar?

This is called citing a secondary source, and it's one of the trickiest citation challenges students face. The good news? Every major citation style has rules for handling this exact situation.

In this guide, you'll learn how to cite secondary sources in APA, MLA, and Chicago format — with clear examples you can follow.

What Is a Secondary Source?

A secondary source is when you quote or reference someone's work that you found mentioned in another source, rather than reading the original work yourself.

For example:

• You're reading Smith's 2020 book
• Smith mentions research by Johnson from 1985
• You want to cite Johnson's idea, but you only read Smith's book

In this case, Johnson (1985) is the primary source (the original), and Smith (2020) is the secondary source (where you actually found it).

When Should You Use Secondary Source Citations?

Secondary source citations should be used sparingly. Only cite this way when:

• The original source is out of print or unavailable
• The original is in a language you can't read
• You cannot access the original through your library
• The original document is extremely rare or restricted

Important: Always try to find and read the original source first. Professors prefer primary sources because:

• The original author's meaning may be misinterpreted
• Context might be lost in the secondary source
• Errors can be introduced when citing secondhand

How to Cite a Secondary Source in APA Format (7th Edition)

APA calls secondary sources "as cited in" citations. You include the secondary source (the one you actually read) in your reference list, and mention both sources in your in-text citation.

APA In-Text Citation Format

Include the original author's name and year, followed by "as cited in" and the secondary source:

Template: (Original Author, Year, as cited in Secondary Author, Year)

Example:

Johnson (1985, as cited in Smith, 2020) found that students who outline their papers write 40% faster.

Or in parenthetical form:

Research shows students who outline write 40% faster (Johnson, 1985, as cited in Smith, 2020).

APA Reference List Entry

Only include the secondary source (the one you actually read) in your reference list:

Smith, A. B. (2020). The complete guide to academic writing. Academic Press.

Key point: Do NOT include Johnson (1985) in your reference list since you didn't read it directly.

APA Secondary Source Example (Complete)

In your paper:

According to Vygotsky's theory of cognitive development (1978, as cited in Brown, 2019), learning is fundamentally a social process. Brown explains that Vygotsky's concept of the zone of proximal development remains influential in modern education.

In your reference list: Brown, M. (2019). Understanding child development: A modern approach. Educational Publishing.

How to Cite a Secondary Source in MLA Format (9th Edition)

MLA handles secondary sources with "qtd. in" (quoted in) notation. Like APA, you only include the secondary source in your Works Cited.

MLA In-Text Citation Format

Use "qtd. in" (quoted in) before the secondary source author:

Template: (Original Author, qtd. in Secondary Author Page)

Examples:

Narrative citation: Johnson argues that "proper citation is the foundation of academic integrity" (qtd. in Smith 45).

Parenthetical citation: Proper citation has been called "the foundation of academic integrity" (Johnson, qtd. in Smith 45).

MLA Works Cited Entry

Only include the secondary source:

Smith, Anna. Academic Writing Essentials. University Press, 2020.

MLA Secondary Source Example (Complete)

In your paper:

Einstein reportedly said that "imagination is more important than knowledge" (qtd. in Isaacson 87). Isaacson provides context for this famous quote, explaining Einstein's belief in creative thinking.

In your Works Cited: Isaacson, Walter. Einstein: His Life and Universe. Simon & Schuster, 2007.

Block Quotes from Secondary Sources (MLA)

For quotes longer than 4 lines, use a block quote:

Johnson describes the research process:

The best researchers approach their topic with curiosity rather than preconceptions. They allow the evidence to guide their conclusions, revising their hypotheses as new information emerges. (qtd. in Smith 112)

Smith notes this advice remains relevant today.

How to Cite a Secondary Source in Chicago Format

Chicago has two styles: Notes-Bibliography (used in humanities) and Author-Date (used in sciences). Both can handle secondary sources.

Chicago Notes-Bibliography Style

In a footnote or endnote, cite the original source, then indicate where you found it:

Footnote format: ¹Original Author, Original Title (Place: Publisher, Year), page, quoted in Secondary Author, Secondary Title (Place: Publisher, Year), page.

Example: ¹John Johnson, Research Methods in Education (Boston: Academic Press, 1985), 45, quoted in Anna Smith, Modern Academic Writing (Chicago: University Press, 2020), 112.

Bibliography entry: Only include the secondary source:

Smith, Anna. Modern Academic Writing. Chicago: University Press, 2020.

Chicago Author-Date Style

Similar to APA, use "cited in":

In-text: (Johnson 1985, cited in Smith 2020, 112)

Reference list: Smith, Anna. 2020. Modern Academic Writing. Chicago: University Press.

Chicago Secondary Source Example (Complete)

In your paper (Notes-Bibliography): As Vygotsky noted, "learning awakens a variety of internal developmental processes."¹

Footnote: ¹Lev Vygotsky, Mind in Society (Cambridge: Harvard University Press, 1978), 90, quoted in James Wertsch, Vygotsky and the Social Formation of Mind (Cambridge: Harvard University Press, 1985), 67.

Bibliography: Wertsch, James. Vygotsky and the Social Formation of Mind. Cambridge: Harvard University Press, 1985.

Common Mistakes When Citing Secondary Sources

Mistake 1: Citing the Original in Your Reference List

Wrong: Including both Johnson (1985) and Smith (2020) in references when you only read Smith.

Right: Only include Smith (2020) since that's the source you actually read.

Mistake 2: Not Indicating It's a Secondary Source

Wrong: (Johnson, 1985) — implies you read the original.

Right: (Johnson, 1985, as cited in Smith, 2020) — clearly shows your actual source.

Mistake 3: Over-Relying on Secondary Sources

Problem: Using too many secondary source citations signals weak research.

Solution: Track down original sources when possible. Use secondary citations only when truly necessary.

Mistake 4: Misquoting Across Sources

Problem: The secondary source may have paraphrased or slightly misquoted the original.

Solution: When possible, verify quotes against the original. If you can't verify, use paraphrasing instead of direct quotes.

Quick Reference: Secondary Source Citation Formats

| Style | In-Text Format | Reference List | |-------|---------------|----------------| | APA | (Author, Year, as cited in Author, Year) | Secondary source only | | MLA | (Author, qtd. in Author Page) | Secondary source only | | Chicago (Notes) | Footnote with "quoted in" | Secondary source only | | Chicago (Author-Date) | (Author Year, cited in Author Year, Page) | Secondary source only |

When to Avoid Secondary Source Citations

Before using a secondary source citation, ask yourself:

1. Can I find the original? Check your library database, Google Scholar, or interlibrary loan.

2. Is the original source essential? If it's a minor supporting point, consider finding a primary source that makes the same argument.

3. Am I using too many? If more than 1-2 citations are secondary, your professor may question your research thoroughness.

4. Is the quote really that important? Sometimes paraphrasing the secondary source's interpretation is better than citing a quote you haven't verified.

Tips for Finding Original Sources

Before citing secondhand, try these strategies:

• Google Scholar — Search the original author and title
• Library databases — JSTOR, ProQuest, EBSCOhost
• Interlibrary loan — Request books/articles from other libraries
• Author's website — Academics often share PDFs of their work
• ResearchGate/Academia.edu — Researchers share papers here
• Contact the author — Scholars often respond to polite requests

FAQ: Secondary Source Citations

Can I cite a source I found in a YouTube video?

Yes, use the same format. The YouTube video is your secondary source. Cite the original author "as cited in" or "qtd. in" the video creator, and include the video in your references.

What if the secondary source doesn't give the original's year?

Write "n.d." (no date) for the original: (Johnson, n.d., as cited in Smith, 2020).

Should I mention I couldn't find the original?

No — the "as cited in" notation already communicates this professionally.

How many secondary sources are too many?

Most professors expect no more than 2-3 secondary source citations in a paper. If you have more, it suggests insufficient research effort.

Can I use a secondary source for a key argument?

Avoid it if possible. Key claims should be supported by primary sources you've read directly.

Conclusion

Citing secondary sources correctly requires you to:

1. Acknowledge both the original author and where you found the information
2. Use the correct format ("as cited in" for APA, "qtd. in" for MLA, "quoted in" for Chicago)
3. Include ONLY the secondary source in your reference list
4. Use secondary citations sparingly

Remember: secondary source citations are acceptable when the original is truly unavailable, but they're not a substitute for thorough research.

---

Write your research paper faster with GenPaper

GenPaper uses AI to help you write papers with real, verified citations. No more manual formatting or citation errors.

Try GenPaper Free →