Background: High-risk sexual behaviours (HRSBs) among young adults are a key risk for Sexually Transmitted Infections (STIs), HIV and unplanned pregnancies. The World Health Organization has identified the 15-24 year age-group as high-risk for STIs. Students at Higher Learning Institutions (HLIs) may be at higher risk because they are free of immediate parental supervision, a transient migratory population, and probably at peak years of sexual activity. Here, we describe risky sexual behaviours and preventive practices among young adults attending HLIs in Mbeya, Tanzania. Methods: Cross-sectional study was conducted from March 2019 to January 2020 among students aged 18-24 years enrolled in HLIs within Mbeya. A self-administered questionnaire was used to collect information on sexual health education, activity, behaviour and STI knowledge. Results: 504 students were enrolled; mean age of 21.5 (SD 1.74) years. 377 (74.8%) students were sexually active. Mean age of first sexual encounter was 18.4 years and 11.6% reported their sexual debut was <15 years. A higher proportion of male students (59.7%) reported their sexual debut with non-steady partners compared with female students (40.9%). Lack of condom use at sexual debut was reported by 43.3% of sexually active students. Consistent condom use during the past 4-weeks was reported at 23.3% and 16.9% among men and women, respectively. Almost 1 in 10 students reported being forced into having sex by someone they were dating. Sex under the influence of alcohol was reported by 25.5% of the students. Nearly 7 in 10 (77%) students had heard of STIs, but only 15% were aware STIs could be asymptomatic. Conclusion: STI prevention programs need to recognize young adults in HLIs as an at-risk population. HLIs must advocate targeted messages to minimize risks to acquiring STIs, offer counselling and support for those experiencing sexual violence, and promote condom use and safer-sex negotiation skills.