Transdermal drug delivery systems, including microneedles (MNs), offer advantages over oral administration by bypassing gastrointestinal degradation and first-pass metabolism, while also reducing injection-associated pain. Hydrogel-forming microneedles (HFMNs) represent a promising advancement in this field as an alternative strategy. This study aimed to develop an HFMN using poly(vinyl alcohol)/poly(N-vinyl caprolactam) (PVA/PNVCL) with citric acid (CA) as crosslinking agent for transdermal delivery of captopril as a drug model. The HFMNs fabrication was optimised by varying crosslinking time, PNVCL concentration, and CA concentration. Evaluations were conducted on physical properties, mechanical strength, insertion ability, in vitro permeation, and drug content. In vivo skin irritation and antihypertensive efficacy tests were also assessed. A crosslinking time of 45 min, CA concentration of 1.0%, and 10% PNVCL significantly increased the insertion ability, swelling index, permeability and mechanical strength of the HFMNs. Among six formulations, F3 (PVA 15%; PNVCL 10%; CA 1%) demonstrated the most promising performance, achieving in vitro permeation of 66.68 ± 2.78%. In vivo studies showed that oral and transdermal delivery of captopril effectively lowered blood pressure in hypertension-induced rats, with transdermal delivery showing superior efficacy, which warrants further clinical investigation. In addition, in the in vivo skin irritation test, it was observed that HFMNs did not cause irritation. The optimised hydrogel-forming microneedles demonstrated enhanced mechanical strength, permeability, and drug delivery performance. Captopril transdermal delivery using PVA/PNVCL-based HFMNs showed superior antihypertensive efficacy compared to oral administration, with no skin irritation observed, supporting its potential for safe and effective clinical application. © The Author(s), under exclusive licence to Controlled Release Society 2026.