We implemented HPTN 062, an acceptability and feasibility study of a motivational-interviewing (MI) intervention to reduce HIV transmission among individuals with acute HIV infection (AHI) in Lilongwe, Malawi. Participants were randomly assigned to receive either brief education or the MI intervention over 24 weeks; all participants received the same messages about AHI. We used mixed methods to assess participants' understanding of the association between AHI and viral load, and its connection to sexual behavior at 8 weeks. While most participants understood key aspects of AHI, MI-intervention participants gave substantially more detailed descriptions of their understanding. Nearly all participants, regardless of study arm, understood that they were highly infectious and would be very likely to transmit HIV after unprotected sex during AHI. Our findings suggest that messages about AHI delivered during the period of AHI are likely beneficial for ensuring that those with AHI understand their level of infectiousness and its association with forward transmission.