To estimate the effect of neighborhood-level modification on the efficacy of the MyPEEPS Mobile intervention on the reduction of condomless anal sex acts among same-sex attracted adolescent men. A series of generalized linear mixed model was used to examine if the effect of the MyPEEPS Mobile intervention on condomless anal sex acts was moderated by neighborhood-level factors using data from the 2019 American Community Survey US Census Bureau. "The magnitudes of intervention were significantly smaller at both 6- and 9-month follow-up among adolescents living in neighborhood with high proportions of Hispanic or Latino residents (IRR6M = 1.02, 95 % CI: 1.01, 1.02; IRR9M = 1.03, 95 % CI: 1.01, 1.05) and high proportions of families with income below the poverty level (IRR6M = 1.07, 95 % CI: 1.01, 1.12; IRR9M = 1.05, 95 % CI: 1.01, 1.10), which indicated that living in communities with a higher concentration of residents living under poverty or of Hispanic/and Latino ethnicity significantly modified the effective of program intervention on condomless sex among adolescent MSM. Understanding how neighborhood characteristics modify the effect of HIV prevention interventions may be useful in better targeting delivery and tailoring content of interventions based on neighborhood level characteristics such as the ones identified in this study.