Use of more effective contraception may lead to less condom use and increased incidence of sexually transmitted infection.The objective of this study was to compare changes in condom use and incidence of sexually transmitted infection acquisition among new initiators of long-acting reversible contraceptives to those initiating non-long-acting reversible contraceptive methods.This is a secondary analysis of the Contraceptive CHOICE Project. We included 2 sample populations of 12-month continuous contraceptive users. The first included users with complete condom data (baseline, and 3, 6, and 12 months) (long-acting reversible contraceptive users: n = 2371; other methods: n = 575). The second included users with 12-month sexually transmitted infection data (long-acting reversible contraceptive users: n = 2102; other methods: n = 592). Self-reported condom use was assessed at baseline and at 3, 6, and 12 months following enrollment. Changes in condom use and incident sexually transmitted infection rates were compared using χ(2) tests. Risk factors for sexually transmitted infection acquisition were identified using multivariable logistic regression.Few participants in either group reported consistent condom use across all survey time points and with all partners (long-acting reversible contraceptive users: 5.2%; other methods: 11.3%; P < .001). There was no difference in change of condom use at 3, 6, and 12 months compared to baseline condom use regardless of method type (P = .65). A total of 94 incident sexually transmitted infections were documented, with long-acting reversible contraceptive users accounting for a higher proportion (3.9% vs 2.0%; P = .03). Initiation of a long-acting reversible contraceptive method was associated with increased sexually transmitted infection incidence (odds ratio, 2.0; 95% confidence ratio, 1.07-3.72).Long-acting reversible contraceptive initiators reported lower rates of consistent condom use, but did not demonstrate a change in condom use when compared to preinitiation behaviors. Long-acting reversible contraceptive users were more likely to acquire a sexually transmitted infection in the 12 months following initiation.