Background and Purpose. It is largely unknown how adaptive motor control of the paretic upper limb contributes to functional recovery after stroke. This paucity of knowledge emphasizes the need for longitudinal 3-dimensional (3D) kinematic studies with frequent measurements to establish changes in coordination after stroke. A portable 3D kinematic setup would facilitate the frequent follow-up of people poststroke. This case report shows how longitudinal kinematic changes of the upper limb can be measured at a patient's home using a portable 3D kinematic system in the first 6 months poststroke. Case Description. The outcomes of the upper-limb section of the Fugl-Meyer Motor Assessment (FMA), the Action Research Arm Test (ARAT), and 3D kinematic analyses were obtained from a 41-year-old man with a left hemispheric stroke. Three-dimensional kinematic data of the paretic upper limb were collected during a reach-to-grasp task using a portable motion tracker in 5 measurements during the first 6 months after stroke. Data from an individual who was healthy were used for comparison. Outcomes. The FMA and ARAT scores showed nonlinear recovery profiles, accompanied by significant changes in kinematic outcomes over time poststroke. Specifically, elbow extension increased, forward trunk motion decreased, peak hand speed increased, peak hand opening increased, and peak hand opening occurred sooner after peak hand speed. Discussion. This case report illustrates the feasibility of frequently repeated, on-site 3D kinematic measurements of the paretic upper limb. Early after stroke, task performance was mainly driven by adaptive motor control, whereas adaptations were mostly reduced at 26 weeks poststroke. The presented approach allows the investigation of what is changing in coordination and how these changes are related to the nonlinear pattern of improvements in body functions and activities after stroke. © 2012 American Physical Therapy Association.