To cite a secondary source in APA style, use the phrase “as cited in” within your in-text citation and include only the secondary source in your reference list. A secondary source is a work you haven’t read directly but found mentioned, quoted, or paraphrased inside another source you did read. The formatting is straightforward once you understand the two-part structure.
What Counts as a Secondary Source
Say you’re reading a 2014 article by Lyon et al., and that article quotes findings from a 1982 study by Rabbitt. You never actually read Rabbitt’s original paper. In this scenario, Rabbitt is the primary source (the origin of the idea), and Lyon et al. is the secondary source (the work you actually have in front of you). APA wants you to be transparent about that distinction so your reader knows exactly what you read and what you’re taking on trust from someone else’s citation.
APA style treats secondary citations as a last resort. If you can reasonably track down the original source and read it yourself, do that and cite it directly. Secondary citations are appropriate when the original work is out of print, unavailable in a language you can read, or otherwise inaccessible. Overusing them can weaken your paper because you’re relying on another author’s interpretation of the original material.
How to Format the In-Text Citation
The in-text citation names the primary source, then uses “as cited in” to connect it to the secondary source you actually read. If you know the publication year of the primary source, include it. Here’s the parenthetical format:
(Rabbitt, 1982, as cited in Lyon et al., 2014)
You can also write it as a narrative citation, weaving the author’s name into your sentence:
Rabbitt (1982, as cited in Lyon et al., 2014) found that…
If the year of the original work is unknown, simply drop it. For example, if you’re referencing Allport’s diary through a book by Nicholson and you don’t know when the diary was written:
Allport’s diary (as cited in Nicholson, 2003)
The key phrase is always “as cited in.” Don’t substitute other wording like “quoted in” or “mentioned in.”
What Goes in the Reference List
Only the secondary source, the work you actually read, gets a reference list entry. The primary source does not appear in your references. Using the example above, you would create a full reference entry for Lyon et al. (2014) but not for Rabbitt (1982). Your reader can then look at your reference list, find the Lyon et al. article, and trace the Rabbitt citation from there if they want to dig deeper.
Format the reference list entry for the secondary source exactly as you would for any other source of its type. If it’s a journal article, use the standard journal article format. If it’s a book, use the book format. The “as cited in” structure only appears in the in-text citation, never in the reference list itself.
Step-by-Step Example
Suppose you’re writing a paper about cognitive decline. You’re reading an article by Lyon, Startup, and Bentall published in 2014, and in that article, they discuss research originally conducted by Rabbitt in 1982. You want to reference Rabbitt’s findings, but you haven’t read Rabbitt’s paper.
Your sentence might look like this:
Earlier research demonstrated significant age-related differences in processing speed (Rabbitt, 1982, as cited in Lyon et al., 2014).
Your reference list would then include only the Lyon et al. entry:
Lyon, H. M., Startup, M., & Bentall, R. P. (2014). Title of the article. Journal Name, volume(issue), page range. https://doi.org/xxxxx
No entry for Rabbitt appears anywhere in your references.
When the Original Year Is Missing
Some primary sources, like personal diaries, unpublished manuscripts, or very old works, don’t have a clear publication year. When that’s the case, leave the year out of the in-text citation entirely. You still name the primary source and use “as cited in” with the secondary source’s author and year. The citation simply has one fewer element:
Allport’s diary (as cited in Nicholson, 2003) revealed…
Don’t insert “n.d.” for the primary source in this situation. Just omit the year.
When to Avoid Secondary Citations
Use a secondary citation only when you genuinely cannot access the original. If the original source is a journal article available through your library’s database, take the time to find it and cite it directly. Direct citations are stronger because you’ve verified the original author’s exact words and context rather than relying on how a second author interpreted or summarized them. Professors and reviewers generally expect secondary citations to be rare in a well-researched paper, not a shortcut for skipping the bibliography chase.