Background and objectives Local pain and painful defecation are common patients’ complaints after anal surgery. Topical diltiazem, a calcium channel blocker, can decrease the tonicity of smooth muscles of anal sphincter and probably decrease the aforementioned painful condition. This study evaluates the efficacy of topical diltiazem gel on these complaints. Methods In this double-blind, randomized, placebo-controlled study, patients received either diltiazem gel or placebo (a gel not containing diltiazem), in inch at the site of operation, twice per day. All patients were followed up on 2nd and 7th postoperative days for scoring of complaints.Results The pain and painful defecation decreased significantly in second day in patients received diltiazem. Pain was completely alleviated in all patients received diltiazem in 7th postoperative day. But, in the placebo group, pain was reported by some of the patients in this day. No unwanted effect was reported in patients received diltiazem. Conclusion Topical 2% diltiazem gel is effective on alleviation of pain and pain during defecation after standard anal surgery.Keyword: Colorectal Surgery, Fissure in Ano, Hemorrhoid, Fistula, Rectum, Diltiazem