This is the third guidance note in a four-part series of notes related to impact evaluation developed by InterAction with financial support from the Rockefeller Foundation.This third guidance note, Introduction to Mixed Methods in Impact Evaluation, starts by explaining what a mixed methods (MM) impact evaluation design is and what distinguishes this approach from quantitative or qualitative impact evaluation designs. It notes that a mixed methods approach seeks to integrate social science disciplines with predominantly quantitative (QUANT) and predominantly qualitative (QUAL) approaches to theory, data collection, data analysis and interpretation. The guidance note is also available in French and Spanish on https://www.interaction.org/impact-evaluation-notes. ATTENTION: ANNEXES 1 TO 11 TO THIS DOCUMENT CAN BE FOUND IN ENGLISH VERSION ON: https://www.interaction.org/introduction-mixed-methods-impact-evaluation-annexes