Author
Last name of the author of the chapter, the initial of the first name. If the chapter has several authors, write them in the same order as in the book.
Year
The year the book was published.
Title of the chapter
The title of the book chapter should not be italicized..
Editors
Write the word In followed by the initial and last name, followed by (Ed.) or (Eds.). End with a comma.
Title
Italicized. For a two-part title, capitalize the first word of the second part of the title: Title: Title.
Pages
Use the abbreviation pp. for pages followed by the page numbers for the chapter in parenthesis with hyphen between the start and the end page.
Publisher
The name of the publisher.
Author, A., & Author, B. (year). Title of chapter. In C. C. Surname (Ed./Eds.), Title of the book (pp. xx-xx). Publisher.
Commentary: Write "In" followed by the editor's or editors' names, and use "Ed." for books with one editor and "Eds." for books with two or more editors within parenthesis. Write the abbreviation "pp." for pages and the pages on where you find the chapter.
Law, M., Polatajko, H., Baptiste, S., & Townsend, E. (2002). Core concepts of occupational therapy. In E. Townsend (Ed.), Enabling occupation: An occupational therapy perspective (2nd ed., pp. 29–56). Canadian Association of Occupational Therapists.
If a book has three authors or more, you only include the first author's name followed by "et al.".
According to one study (Law et al., 2002) it is clear that ...
To cite a book chapter is a bit different from citing a whole book in that you refer to a part (the chapter) of a whole (the whole book in where you find the chapter). This way of referencing is similar to how you reference a journal article which is also a part (the article) of a whole (the journal issue). Therefore, it is the whole, i.e. the title of the whole book, that is italicized, not the part (the article).
Further reading on how to write references for book chapters on APA Style: Edited Book Chapter References