Background: Patient-Reported Outcome Measures (PROMs) are tools of increasing interest in the sports population. The purpose of this study was to perform the cross-cultural adaptation and reliability analysis of the 4 Domain Sports Patient-Reported Outcome Measure (4 DSP) into Spanish. Methods: A six-stage cross-cultural adaptation protocol was executed to obtain the Spanish version of the 4 DSP (S-4DSP). Subsequently, the questionnaire was administered to a population of 108 postoperative athletes with ACL (Anterior Cruciate Ligament) injuries. The questionnaire was administered again after 30 days. Acceptability, floor and ceiling effects, internal consistency (Cronbach's alpha), and reproducibility (Intraclass Correlation) were evaluated. Results: The S-4DSP was fully completed by 108 participants (mean age 34 ± 10.75, 26% women), achieving 100% acceptability. No floor effect was detected. The statistical analysis yielded a global Cronbach's alpha for the questionnaire of 0.65, and domain-specific alphas of 0.88, 0.72, 0.27, and 0.68 for the first, second, third, and fourth domains, respectively. The Intraclass Correlation test reached a maximum of 0.94 and a minimum of 0.48 for the first and fifth questions, respectively. Conclusions: The S-4DSP is a reliable and useful tool for evaluating Spanish-speaking athletes after ACL reconstruction.