We investigate mutations and correlates according to HIV-1 subtype after virological failure (VF) of standard first-line antiretroviral therapy (ART) (non-nucleoside/nucleotide reverse transcriptase inhibitor [NNRTI] +2 nucleoside/nucleotide reverse transcriptase inhibitor [N(t)RTI]). SECOND-LINE study participants were assessed at baseline for HIV-1 subtype, demographics, HIV-1 history, ART exposure, viral load (VL), CD4(+) count, and genotypic ART resistance. We used backward stepwise multivariate regression (MVR) to assess associations between baseline variables and presence of 3 N(t)RTI mutations, 1 NNRTI mutation, 3 thymidine analog-N(t)RTI [ta-N(t)RTI] mutations (TAMs), the K65/K70 mutation, and predicted etravirine (ETV)/rilpivirine (RPV) activity. The inclusion p-value for MVR was p<.2. The exclusion p-value from stepwise elimination was p>.05. Of 541 participants, 491 (91%) had successfully characterized baseline viral isolates. Subtype distribution: B (n=123, 25%), C (n=202, 41%), CRF01_AE (n=109, 22%), G (n=25, 5%), and CRF02_AG (n=27, 5%). Baseline CD4(+) 200-394 cells/mm(3) were associated with <3 N(t)RTI mutations (OR=0.47; 95% CI 0.29-0.77; p=.003), absence of the K65/K70 mutation (OR=0.43; 95% CI 0.26-0.73; p=.002), and higher ETV sensitivity (OR=0.52; 95% CI 0.35-0.78; p=.002). Recent tenofovir (TDF) use was associated with K65/K70 mutations (OR=8.91; 95% CI 5.00-15.85; p<.001). Subtype CRF01_AE was associated with 3 N(t)RTI mutations (OR=2.34; 95% CI 1.31-4.17; p=.004) and higher RPV resistance (OR=2.13; 95% CI 1.30-3.49; p=.003), and subtype C was associated with <3 TAMs (OR=0.45; 95% CI 0.21-0.99; p=.015). Subtypes CRF01_AE (OR=2.46; 95% CI 1.26-4.78; p=.008) and G (OR=4.77; 95% CI 1.44-15.76; p=.01) were associated with K65/K70 mutations. Higher VL at confirmed first-line VF was associated with 3 N(t)RTI mutations (OR=1.39; 95% CI 1.07-1.78; p=.013) and 3 TAMs (OR=1.62; 95% CI 1.15-2.29; p=.006). The associations of first-line resistance mutations across the HIV-1 subtypes in this study are consistent with knowledge derived from subtype B, with some exceptions. Patterns of resistance after failure of a first-line ta-N(t)RTI regimen support using TDF in N(t)RTI-containing second-line regimens, or using N(t)RTI-sparing regimens.