Background: Although use of Electronic Nicotine Delivery Systems (ENDS) is increasingly prevalent among young adults, little is known about predictors of ENDS initiation among this population. Aims: We examined the roles of the social environment (i.e., peer ENDS use and household ENDS use), normative beliefs (i.e., social acceptability of ENDS use), and attitudes (i.e., inclination to date someone who uses ENDS) in prospectively predicting initiation of ENDS over a 1-year period among 18- to 29-year-old college students. Method: Participants were 2,110 (18- to 29-year-old) students (M = 20.27, SD = 2.17) from 24 colleges in Texas who participated in a three-wave online survey, with 6 months between each wave. All participants reported never using ENDS at baseline. A multivariable, multilevel logistic regression model, accounting for clustering of students within colleges, was used to assess if students' social environment, normative beliefs, and attitudes predicted subsequent initiation of ENDS up to 1 year later, adjusting for various sociodemographic factors and number of other tobacco products used. Results: In all, 329 college students (16%) initiated ENDS within 1 year. Results from the logistic regression indicated that college students who were younger (18-24 years old), ever used other tobacco products, indicated a more dense peer network of ENDS users, and had a higher inclination to date someone who uses ENDS had higher odds of initiating ENDS than their peers. Conclusion: Preventing ENDS initiation should be included in college health promotion programs, which should highlight the roles of students' social environment and attitudes regarding ENDS use.