This paper presents the results of investigations of C45 steel with a ferrite-pearlite microstructure obtained by austenitizing at 850°C, accelerated cooling in compressed air, and subsequent subcritical heat treatment below Ac₁. The applied route is therefore described as accelerated air cooling followed by subcritical holding, and not as classical quenching and tempering of martensite. The specimens were held at 500, 550, 600, 650, and 700°C for 15 min, 1 h, 3 h, 9 h, and 23 h. Tensile testing was used to determine the yield strength Re, ultimate tensile strength Rm, and elongation A, while Vickers microhardness HV0.5 and SEM observations were used to characterize the response of the material. The results showed a monotonic decrease in Re, Rm, and HV0.5 with increasing subcritical heat-treatment temperature and holding time, whereas elongation generally increased, although with local non-monotonic variations. The observed trends are interpreted as consistent with softening processes in a ferrite-pearlite structure; however, because the metallographic evidence is qualitative, the mechanistic interpretation is formulated cautiously. The presented data may support the selection of subcritical heat-treatment parameters for C45 steel when specified tensile properties and hardness are required.