This study examined methamphetamine use among people who inject heroin in Hai Phong, Vietnam, using survey data collected from more than 4,000 participants between 2016 and 2018. It explored trends in methamphetamine initiation and current use, related risk behaviors, and implications for public health. The findings highlighted the rapid rise of methamphetamine use since the mid-2000s and discussed the potential role of community-based harm reduction approaches in addressing methamphetamine use in the absence of widely accessible treatment options.