Background: Forward head posture (FHP) has become increasingly common owing to the widespread use of digital devices and sedentary work environments. This postural deviation leads to muscle imbalances, increased cervical and shoulder tension, and reduced range of motion (ROM). Various exercises and Transfer Electrode Capacitive and Resistive (TECAR) therapy are frequently used to address FHP-related problems. However, direct comparisons of their immediate effects remain limited. Objects: This study aimed to compare the immediate effects of TECAR therapy and self-exercise (SE) on cervical ROM, muscle tone, and rounded shoulder posture in patients with FHP. Methods: Thirty adults with FHP were randomly assigned to either the TECAR therapy group (n = 15) or the SE group (n = 15). Each group received one 20-minute session. The TECAR group underwent capacitive- and resistive-mode treatments applied to the cervical and shoulder regions to promote thermal relaxation. The SE group performed supervised stretching of the sternocleidomastoid (SCM), upper trapezius, scalene, and pectoralis major (PM); shoulder shrugs; chin tucks; and isometric neck exercises. Cervical ROM, muscle tone, and acromion-totable distance (ATD) were measured before and after the intervention. Statistical analyses were performed using paired and independent t-tests with α = 0.05. Results: Both interventions significantly improved cervical ROM, muscle tone, and ATD (p < 0.05). The TECAR group showed greater improvements in left lateral flexion ROM (p = 0.015), greater reductions in right SCM (p = 0.012) and left PM tone (p = 0.024), and greater correction of right-sided ATD (p = 0.036) than the SE group. Conclusion: TECAR therapy and SE effectively improved cervical mobility, reduced muscle tone, and corrected postural misalignment in patients with FHP. TECAR therapy demonstrated superior short-term effects in promoting muscle relaxation and alignment, supporting its value as an adjunct to exercise-based rehabilitation.