Performance of a passively cooled thermoelectric generator (TEG) under different operating conditions is experimentally investigated in this study. The effect of input heat rate in addition to the influence of utilizing various passive heat dissipation techniques on the TEG performance are analyzed and demonstrated. The temperature of the TEG sides, power output, conversion efficiency and the response time (i.e., the time required to reach steady state operation) are accounted as a denotation to the characteristics of the TEG performance. Free convection (FC), passive water cooling (PWC) and vapor phase change cooling (VPC) are employed for heat dissipation from the TEG through the cold side. Also, the effect of utilizing finned heat sink (fins) and the effect of filling ratio (i.e., in case of utilizing PWC and VPC) on the performance of the employed heat dissipation techniques are explored. From the experimental results, it can be deduced that increasing the input heat rate and utilizing fins to aid heat dissipation have enhanced the TEG performance and provided higher power output for all other operating conditions studied. VPC aided by fins showed the best performance compared to other techniques exploited. Additionally, the results illustrated that in case of employing PWC and VPC, it is necessary to use an optimal filling ratio for the working fluid utilized in order to achieve the best performance. The experimental data obtained are compared with the data available by the TEG module manufacturer and excellent agreement is obtained.