A polyolefin resin composition (A) comprising 1 to 99 wt.% 1-butene polymer, 99 to 1 wt.% propylene resin, and at least 10 ppm nucleating agent; a film obtained by forming the composition (A); and a multilayer structure in which at least one of the outermost layers comprises a polyolefin resin composition (B) comprising 1 to 99 wt.% 1-butene polymer and 99 to 1 wt.% propylene resin. The 1-butene polymer is a crystalline resin having a melting point of 0 to 100 DEG C and has a stereoregularity index, (mmmm)/(mmrr+rmmr), of 20 or lower, a molecular-weight distribution, Mw/Mn, of 4.0 or lower, and a weight-average molecular weight, Mw, of 10,000 to 1,000,000. The film formed from the composition (A) is excellent in transparency and flexibility and has an improved rate of crystal stabilization. The multilayer structure is improved in low-temperature heat sealability and hot tack.