Background Early identification of treatment response is clinically important in psoriasis management, as it may facilitate timely treatment modification and reduce exposure to ineffective therapies. Although early improvement in the Psoriasis Area and Severity Index (PASI) has been associated with long term outcomes for individual therapies, a broadly applicable early PASI threshold across different treatment modalities in real-world practice remains unclear. Objectives To evaluate the predictive value of early PASI improvement for subsequent PASI90 achievement across multiple psoriasis treatment modalities and to identify a clinically meaningful early PASI response threshold applicable in routine clinical practice. Methods This prospective, multicenter real-world cohort study included adult patients with moderate-to-severe plaque psoriasis receiving methotrexate, phototherapy, IL-17 inhibitors, or IL-23 inhibitors. Receiver operating characteristic (ROC) curve analyses were used to evaluate the predictive performance of week-4 PASI improvement for achieving PASI90 at 3 months and 6 months. The optimal early response threshold was identified using the Youden Index. Multivariable logistic regression analyses were conducted to assess the independent association between early PASI response and subsequent PASI90 achievement. Results A total of 2,023 patients were included in the analysis. The optimal week-4 PASI improvement threshold for predicting PASI90 at 3 months was 62% for IL-17 inhibitors, 62% for IL-23 inhibitors, 59% for methotrexate and 61% for phototherapy. Multivariable logistic regression analyses further demonstrated that a PASI improvement of approximately 60% at week 4 was independently associated with a higher likelihood of achieving PASI90 at 3 months. Conclusions Achieving PASI60 at week 4 serves as a consistent and broadly applicable early indicator of subsequent PASI90 response across multiple psoriasis treatment modalities. Incorporating this threshold into early treatment assessment may help inform individualized treatment decisions and optimize outcomes in real-world management of moderate-to-severe psoriasis.