Post-exposure prophylaxis (PEP) is a biomedical approach to HIV prevention that is administered after a potential exposure to the virus. Although it was originally approved in the UK for occupational exposure to HIV among healthcare workers, PEP has remained a controversial method of preventing HIV infection following sexual exposure. To examine emerging social representations of PEP, we undertook a qualitative thematic analysis of 72 articles published in UK newspapers between 1997 and 2015. We focused on print media, as they still reflect broader societal debates, set the agenda for wider discussions in other media and contribute to shaping public perceptions and policy priorities. Our findings show that there were two major social representations of the use of PEP for HIV prevention amongst gay and bisexual men: a positive social representation of PEP as a relatively straightforward solution, where PEP is metaphorically framed as the ‘morning-after pill’, and a more negative social representation of PEP as posing risks and yielding uncertain outcomes. We also found a third social representation for the use of PEP amongst public health care workers, where PEP is represented as needed and deserved. The positive representation generally consisted of anecdotal statements, while the negative representation was substantiated by ‘expert’ and layperson voices, rendering the latter more akin to a hegemonic representation of PEP. We generally found a lack of technical information in all newspapers, and an information gap that might inhibit informed discussion and lead to entrenching polarised social representations and to the stigmatisation of some users of PEP.