爆炸发生后，美国司法部调查局（联邦调查局前身）和当地警方立即展开调查。起初，调查並没有将爆炸和恐怖主义联系起来。调查员对这种欠缺特定襲擊目标造成无辜路人死傷的行动感到疑惑，特别是建筑物也仅受到相对轻微、非结构上的破壞。纽约地区助理检察官认为爆炸时间、地点和爆炸物的佈置方式显示华尔街和J.P.摩根公司是爆炸的目标，因此可能是激进反对资本主义的布尔什维克、无政府主义者、共产主义者和社会主义者等組織所為[1]:150-151。9月17日，司法部调查局公开了爆炸前在华尔街的一个邮箱内发现的传单。传单是一张白纸上使用红色墨水书写的文字和署名：“记住，我们不会再忍耐了。释放政治犯，否则你们全都要去死。美国无政府主义斗士。”[注 2]时任司法部调查局长威廉·J·弗林（英语：William J. Flynn）认为这张传单和1919年美国无政府主义连环爆炸中发现的传单十分相似[1]:171-175[5]，从而迅速确认爆炸不是一场意外。官方消息谴责了无政府主义者和共产主义者。华盛顿邮报称这一爆炸是“宣战的行为”[6]。
调查员还讯问了曾在四届美国网球大奖赛中获得双打冠军的埃德温·P·费舍尔（英语：Edwin P. Fischer）。他曾在爆炸发生前向友人寄送警告明信片，让其在9月16日之前远离这一区域。他告诉警方是“从空气中”收到这一消息。然而，他们发现发送警告明信片是费舍尔的惯常行为，并将其移交一家精神病院。费舍尔被诊断出患有精神病，但是没有伤害性[8][9]。
這次爆炸事件啟發了幾本著作，特別是Beverly Gage的《The Day Wall Street Exploded》、傑德·魯本菲爾德（英语：Jed Rubenfeld）的《The Death Instinct》和邁克·戴維斯（英语：Mike Davis (scholar)）的《Buda's Wagon: A Brief History of the Car Bomb》。
^原文："Remember, we will not tolerate any longer. Free the political prisoners, or it will be sure death for all of you. American Anarchist Fighters."[1]:171-175
^原文："such as the Union of Russian Workers, the I.W.W., Communist, etc....and from the result of the investigations to date it would appear that none of the aforementioned organizations had any hand in the matter and that the explosion was the work of either Italian anarchists or Italian terrorists."[1]:325
^原文："Buda was a real militant, capable of anything. In 1933 I drove to New York with Buda's nephew, Frank Maffi...Frank said, 'Let's drive downtown and see my uncle's bomb', and he took me to Wall Street, where the big explosion took place in September 1920, just before Buda sailed for Italy. You could still see the holes in the Morgan building across the street."[3]:133
^Balousek, Marv; Kirsh, J. Allen. 50 Wisconsin Crimes of the Century. Badger Books Inc. 1997: 113. ISBN 978-1-878569-47-9（英语）. The 1917 bomb used black powder with a homemade sulfuric acid/metal plate "time" fuse, which failed to explode until the package was opened at the police station. By 1920, it is notable that Galleanist bombmaker(s) had apparently discontinued the use of the unreliable acid detonators in favor of dynamite with an electric blasting cap and a clock wired to a battery as a timed detonator.
