The Familias Unidas intervention is an efficacious family-based preventive intervention for reducing substance use and other health risks among Hispanic youth. A current randomized controlled trial (RCT) is examining this intervention’s efficacy when delivered via the Internet ( eHealth ). eHealth interventions can overcome logistical barriers to participation, yet there is limited information about the feasibility of these interventions, especially among ethnic minorities. This paper examines participation and predictors of participation in the eHealth Familias Unidas intervention in a sample of 113 Hispanic families whose adolescent had behavioral problems. Analyses examined multidimensional ways of characterizing participation, including the following: (1) total intervention participation, (2) initial engagement (participating in at least one of the first three intervention sessions), (3) completing the pre-recorded, eHealth parent group sessions, and (4) participating in the live, facilitator-led, eHealth family sessions. Participation in this eHealth intervention was comparable to, and in most cases higher than, previous, face-to-face Familias Unidas interventions. High levels of baseline family stress were associated with lower initial engagement and lower family session participation. Greater parental Hispanicism was associated with more participation in eHealth parent group sessions and across the total intervention. Higher levels of baseline effective parenting, in other words less intervention need, were significantly associated with lower levels of total intervention participation and lower levels of family session participation. Implications for preventive interventions delivered via Internet are discussed.