Do I need to indicate a paragraph break when quoting prose?

Note: This post relates to content in the eighth edition of the MLA Handbook. For up-to-date guidance, see the ninth edition of the MLA Handbook.

No. Unlike quotations of poetry, quotations of prose do not need to communicate the layout of the text. Thus, if you quote the last line of one paragraph and the first line of the next, you do not need to mark the paragraph break in any way. But since the start of a new paragraph generally indicates a shift to a new idea, you might consider quoting each sentence separately.