Provided are: a thermosetting resin composition, for use in an organic material suited to high frequency use, that has outstanding low dielectric tangent, heat resistance, flexibility, and ease of workability; a thermosetting resin sheet; an electronic component; and an electronic device. The present invention is a thermosetting resin composition that includes the following constituents (A1)-(C). (A1) Polyimide resin: a polyimide resin including a diamine residue with formula (8) and/or formula (9) (in formula (8), a, b, c, and d are integers 1 or greater that meet the conditions a+b=6-17 and c+d=8-19, and the dashed lines denote carbon-carbon single bonds or carbon-carbon double bonds) (in formula (9), e, f, g, and h are integers 1 or greater that meet the conditions e+f=5-16 and g+h=8-19, and the dashed lines denote carbon-carbon single bonds or carbon-carbon double bonds). (B) Phenylene ether resin: a phenylene ether resin that has a number average molecular weight of 500-5,000 and, at a terminal of a molecular chain, includes at least one cross-linked functional group selected from the group consisting of a phenolic hydroxyl group, an acryl group, a vinyl group, and an epoxy group. (C) Maleimide resin: a maleimide resin.