Beef-on-dairy (BoD) calves are increasingly common on dairy farms, yet little is known about their behavior or how social housing with purebred dairy calves may influence behavioral responses. This study evaluated the effects of breed composition (Holstein vs. BoD [Angus × Holstein]) and pair composition on behavior and behavioral responses in standardized tests. In Study 1 (n = 26; 18 Holstein, 8 BoD), calves were observed using scan sampling (5 d/wk) for behaviors including exploration, feeding, play, and abnormal oral behavior. A food neophobia test was conducted at 50 d of age. In Study 2 (n = 62; 37 Holstein, 25 BoD), calves were housed in Holstein, mixed, or BoD pairs. Behavioral observations were conducted weekly for 1 h around milk meals. Calves also underwent behavioral tests: food neophobia (19 ± 2 and 48 ± 2 d), novel object (16 ± 3 and 41 ± 2 d), novel human approach (65 ± 3 d), and regrouping (79 ± 2 d). Breed composition affected exploration (P<0.01) and feeding (P<0.01) behaviors: Holsteins explored more, whereas BoD calves performed more feeding behaviors. In the novel food test, Holsteins interacted less (OR: 0.28; 95% CI: 0.07–0.92; P=0.03), took longer to touch (P=0.04), and consumed less novel food than BoD calves (Holstein: 2.17 ± 0.96 g; BoD: 6.55 ± 1.89 g; P=0.03), while in the novel object test, they interacted more frequently (P=0.01), with similar latencies. Pair composition also affected calf behavior, particularly in Holstein calves housed with BoD peers. These calves showed increased feeding behavior (P < 0.001), greater abnormal oral behaviors (P < 0.01), and longer latencies to approach an unfamiliar human compared with Holstein calves housed in homogeneous pairs. Overall, breed composition and pair composition shaped preweaning calf behavior, with mixed housing positively influencing feeding behavior but negatively affecting oral behaviors.