Breast cancer (BC) surgery often reduces upper limb range of motion (ROM), negatively affecting quality of life. Since most research focuses on early recovery, this study investigates differences in ROM between the surgical (SA) and non-surgical (NS) arms in BC survivors and between recent (2.5 years—NR) surgery groups. Upper limb kinematics (flexion–extension, abduction, internal–external rotation) were recorded using inertial measurement units in 26 BC survivors (age: 48.92 ± 7.89 years; stature: 1.57 ± 0.05 m; mass: 66.59 ± 14.07 kg; BMI: 27.14 ± 5.71 kg/m²). ROM, angular velocity, and movement smoothness were analyzed. The SA group demonstrated reduced ROM during flexion (p = 0.023) and extension (p = 0.005) compared to the NS group. Within the RS group, the SA group exhibited lower ROM (p = 0.005), reduced peak angular velocity (p = 0.008), and average angular velocity (p = 0.006) during extension compared with the NR group. Additionally, the average extension angular velocity of the arm among the NS group was higher in the RS group than in the NR group. BC surgery causes persistent upper limb kinematic impairments, mainly during flexion and extension, which can be observed up to six years after surgery. Therefore, early and continuous tailored physical exercise is highly recommended to mitigate these long-term functional deficits.