The exposure of human children to smartphone radiation has been rapidly increasing in the past few years because of the development of smartphones and smartphone networks. Additionally, global crises, such as COVID-19 lockdown, dramatically escalated electronic consumption of each individual human. Due to the relatively small head size, different anatomical structure, and different electromagnetic properties, a child head is expected to react differently to exposure to electromagnetic radiation compared to an adult head. This study presents a computational analysis of Specific Absorption Rate (SAR) and temperature distributions inside anatomical 7-year-old child head model exposed to sub-6 GHz fifth-generation mobile phone radiation. Four different frequencies (0.9 GHz, 1.8 GHz, 3 GHz, and 6 GHz) as well as two antenna positions (voice and video call) were investigated. Electromagnetic wave propagation equations and thermal energy balance equation were numerically solved inside the computational space with 1W antenna power. It is observed that for 6 GHz frequency in voice call position, peak SAR and temperature values of 22.5 W/kg and 8.14 °C, respectively, were obtained. However, the peak SAR and temperature points locations were not correlated. Also, peak temperature elevation surpassed 90% of its ultimate value within the first 5 minutes of exposure time.