Background/Objectives: The Kerlan-Jobe Orthopaedic Clinic Shoulder & Elbow Score (KJOC) is used to identify dysfunctions and estimate injury risk in overhead sports athletes. Although it has been validated in several countries, a European Portuguese version is currently unavailable. This study aimed to translate, culturally adapt and assess psychometric properties (validity and reliability) of the European Portuguese KJOC (KJOC-PT). Methods: The KJOC-PT was translated and culturally adapted according to international guidelines. One hundred athletes were selected (median age 24 [IQR 17] years, 72% male) and divided into two groups: asymptomatic and symptomatic athletes. The convergent validity was assessed by correlating the KJOC-PT with the Disabilities of the Arm, Shoulder and Hand (DASH) and DASH-Sports. 31 athletes from the initial sample were considered to assess between-day reliability and agreement (Bland-Altman analysis). Floor and ceiling effects were also calculated. Sampling adequacy was assessed using the Kaiser Meyer-Olkin (KMO) test. Results: Minor cultural and linguistic changes were made in the KJOC-PT. This version demonstrated excellent internal consistency (Cronbach’s α = 0.91 to 0.97) and moderate negative correlations for validity (KJOC-PT with DASH, rho = −0.595; with DASH-Sports, rho = −0.533, both p < 0.001). Good reliability (ICC_2,1 = 0.77 to 0.89 [95%CI 0.36 to 0.96]), measurement error (SEM = 4.11 to 6.90; MDC = 11.39 to 19.13) and mean difference ranging from −0.08 ± 6.14 to 3 ± 9.17 were found. No floor effect (0%) and ceiling effects of 24.2% for the total sample (50% for asymptomatic and 5.1% for symptomatic athletes) were found. Conclusions: KJOC-PT is now available and is a valid and reliable instrument for use by athletes in overhead sports.