Background: Competitive DanceSport imposes substantial cardiovascular demands, yet heart rate (HR) responses to pair and solo performance of Standard dances have rarely been examined within the same dancers. This study compared mean HR (HRmean) and peak HR (HRpeak) between a solo session and a subsequent pair session across the five Standard dances. Methods: Sixteen competitive Standard dancers (eight established couples; performance class A–S, Slovak Dance Sport Federation; age 22.5 ± 2.6 years) completed two simulated competition finals one week apart, first individually and then with their regular partner; condition was therefore confounded with session order. Each final comprised Waltz, Tango, Viennese Waltz, Slow Foxtrot, and Quickstep, performed for 90 s at competition-prescribed tempos. HR was recorded with Polar H10 chest straps. Overall effects were analyzed with linear mixed models accounting for repeated observations within dancers and potential dependence within couples; pair–solo differences within dances were estimated with paired t tests, and distribution-free and couple-level analyses served as sensitivity analyses. Results: HRmean was higher in the pair session by 8.9 beats·min⁻¹ (95% CI 5.0–12.8; p < 0.001) and HRpeak by 7.5 beats·min⁻¹ (95% CI 3.8–11.2; p < 0.001). In exploratory dance-specific comparisons (Condition × Dance, Greenhouse–Geisser-corrected: HRmean p = 0.008; HRpeak p < 0.001), differences ranged from 11.1 (Tango) to 5.8 beats·min⁻¹ (Quickstep) for HRmean and from 10.9 (Waltz) to 3.9 beats·min⁻¹ (Quickstep) for HRpeak. For HRpeak in Quickstep, the paired estimate was 3.9 beats·min⁻¹ (95% CI 1.0–6.7; Holm-adjusted p = 0.014), whereas the mixed model with a pooled residual variance gave a 95% CI of −0.01 to 7.76 (p = 0.0504). Couple-level analyses and distribution-free tests supported the overall findings. Conclusions: HRmean and HRpeak were higher in the pair session than in the preceding solo session; the variation across dances was exploratory. Because condition was confounded with session order, these differences cannot be attributed to partner interaction.