The conventional transcatheter closure of patent ductus arteriosus (PDA) requires femoral artery puncture and angiography for duct anatomic and shunting estimation. If such estimation can be replaced by transthoracic echocardiography (TTE), the procedure will be further simplified, with fewer invasions. This study aimed to examine whether TTE can serve as an alternative to aorta angiography and as a major guidance for transcatheter duct closure. The study enrolled 298 consecutive patients (71 males and 227 females) with PDA. In the study, TTE with combined two-dimensional echocardiography (2DE) imaging and color-coded flow imaging (CDFI) was performed to measure the minimal shunting width (MSW) as the estimated minimal duct size for selection of an Amplatzer duct occluder (ADO) and to monitor the transcatheter duct closure intraprocedurally. The MSW was validated against the duct-stretched diameter (SDD), against the minimal waist diameter of the conical part of a released occluder measured by X-ray spot picture after successful duct closure (SDC), and against the size of the finally used ADO (SADO). Good correlation was found between MSW and SDD [SDD (mm) = 1.31 MSW; r = 0.89; p < 0.01] and between MSW and SADO [SADO (mm) = 1.71 MSW; r = 0.88; p < 0.01]. Of 296 patients who received occlusion using MSW as the reference for selection of the occluder, SDC was attained in 288 (97.3%), 5 (1.7%), and 2 (0.7%) patients, respectively, at the first, second (1 ADO replacement), and third (2 ADO replacements) occluding attempt. Acute occluder dislodgement occurred in one patient (0.3%). At the 12-month follow-up assessment, no major complications were found, and the total immediate or 12-month SDC was 99.7%. Echocardiography as an alternative major guidance to angiography for transcatheter duct closure is technically feasible, and TTE guidance can further simplify the procedure, with fewer invasions and potential complications.