Altitude training is a common strategy used with the intent to increase hemoglobin mass (Hbmass) in athletes. However, if the Hbmass is increased during altitude camps it seems to decline rapidly upon returning to sea level. This study aimed to examine the efficacy of three weekly heat training sessions over a 3.5-week period following a 3-week altitude camp, on the maintenance of Hbmass in elite cyclists. Eighteen male cyclists (maximal oxygen consumption: 76 ± 5 mL·min-1·kg-1) underwent a 3-week altitude training camp at ~2100 m above sea level. After the camp, participants were divided into one group performing three weekly heat sessions that was subtracted from their usual training (HEAT) while the other continuing usual training (CON). Training characteristics were recorded during the intervention, while hematological measurements were recorded before the camp as well as two days and 3.5-weeks after the altitude camp. The 3-week altitude camp led to an overall increase in total Hbmass of 4.1%. Afterwards, HEAT maintained Hbmass (0.2%, p = 0.738), while CON group experienced a significant reduction (-3.3%, p < 0.001) (ΔHEAT vs. ΔCON, p < 0.001). Moreover, HEAT increased plasma volume (PV) by 11.6% (p = 0.007) and blood volume (BV) by 5.8% (p = 0.007), whereas CON only showed an increase in PV (5.5%, p = 0.041). Exercise intensity and training load were not different between groups during the maintenance period. This study suggests that incorporating three weekly heat training sessions into the usual training routine preserves a moderately increased Hbmass in elite cyclists following an altitude camp.