Athletes require heat acclimation protocols that can be both flexible and integrative, whilst still being effective in inducing hallmark adaptations. We hypothesised that post-exercise sauna bathing 1) could be interspersed across a seven-week training period as a form of long-term heat acclimation, and 2) would be increasingly effective in inducing hallmark heat acclimation adaptations (i.e., reduced rectal temperature [Trec], heart rate [HR], sweating [indexed via body mass loss and sweat gland activation], perceived exertion [RPE] and thermal perception) when assessed after 3 and 7 weeks. Six trained middle-distance runners (3 female; mean±SD; age 19±1 years, VO2max 60.2±10.1 ml.kg-1.min-1) performed a running heat tolerance test (30-minutes, 9 kph/2% gradient, 40°C/40%RH; RHTT) before (RHTTPRE), following 3-weeks (RHTT3W) and following 7-weeks (RHTT7W) endurance training with 30-minutes post-exercise sauna bathing (101-108°C) 3±1 times per week. Data were analysed using a one-way ANOVA, with Bonferroni-corrected post hoc comparisons. To assess ordinal data, Friedman’s test was performed with post hoc analysis by Wilcoxon sign-rank tests. Resting Trec was lower (main effect: p=0.010) at 3 weeks (-0.2±0.1°C; p=0.036) and 7 weeks (-0.2±0.2°C; p=0.038) as compared to pre-acclimation. Peak Trec was lower (main effect: p<0.001) during RHTT3W (-0.3±0.2°C; p=0.043) and RHTT7W (-0.4±0.2°C; p=0.006), as compared to RHTTPRE. Furthermore, peak Trec during RHTT7W was lower than that during RHTT3W (-0.1±0.1°C; p=0.038). Peak RPE was lower (main effect: p=0.042) in RHTT7W only, both in comparison to RHTTPRE (-3±3 pts; p=0.043) and in comparison to RHTT3W (-1±1 pts; p=0.034). There was a main effect of time on peak HR (p=0.022; RHTTPRE: 160±20 bpm, RHTT3W: 149±20 bpm, RHTT7W: 151±15 bpm), whole-body sweat loss (p=0.043; RHTTPRE: 0.9±02 kg, RHTT3W: 0.8±0.1 kg, RHTT7W: 0.8±0.2 kg), and sweat gland activation on the forearm (p=0.039; RHTTPRE: 42±15 active glands/cm2, RHTT3W: 69±9 active glands/cm2, RHTT7W: 69±13 active glands/cm2), though these differences could not be located post hoc. Thermal comfort did not significantly change (p=0.072; mean ratings between “Uncomfortable” and “Slightly Uncomfortable”), nor did ratings of thermal sensation (p=0.115; mean ratings between “Hot” and “Warm”). These data indicate that some hallmark adaptations of heat acclimation can be observed following 3-weeks intermittent post-exercise sauna bathing (i.e. resting and exercising rectal temperatures), with some further development occurring with longer (i.e. 7-weeks) exposure. Changes in perceived exertion were only observed following 7-weeks exposure. Further investigation is required to determine the effect of intermittent post-exercise sauna bathing on cardiovascular and sudomotor outcomes.