Purpose To report surgical outcomes of microcatheter-assisted trabeculotomy following failed angle surgeries, and compare those with no previous angle surgery, in primary congenital glaucoma (PCG). Methods The early postoperative (12 months) results of 42 eyes of 36 patients who underwent microcatheter-assisted trabeculotomy by single surgeon for PCG were retrospectively analyzed. Group 1, 20 eyes of 16 patients, had no previous angle surgery. Group 2, 22 eyes of 20 patients, had one or two previous failed angle surgeries. Success was defined as an intraocular pressure (IOP) < 21mm Hg with at least a 30% reduction from preoperative IOP with (qualified success) or without (complete success) the use of antiglaucoma medication. Results Mean IOP decreased from 31.5 +/- 7.2 mm Hg on 3 (median, range: 1-5) medications in Group 1 and 34.6 +/- 7.3 mm Hg on 3 (median, range: 1-4) medications in Group 2 preoperatively to 15.6 +/- 3.1 mm Hg on 0 (median, range: 0-4) medications in Group 1 and 16.0 +/- 4.6 mm Hg on 0 (median, range: 0-2) medications in Group 2 postoperatively at 12 months (both P<0.001), respectively. The mean percentage of IOP reduction from preoperative to last postoperative visit was 46.0 +/- 20.1% in Group 1 and 45.5 +/- 25.0% in Group 2, P= 0.947. Qualified and complete successes were comparable between Group 1 and Group 2 (qualified success: 90.0% vs 77.3%, P= 0.294; complete success: 78.9% vs 77.3%, P= 0.853). Complications were minimal. Conclusions Microcatheter-assisted trabeculotomy achieved significant pressurelowering effects with a reduction in medication use in PCG, and it represents a reasonable choice of initial and repeat surgical treatment for PCG.