We report a study of the recombination of H3+ (v = 0) ions with thermal electrons at 330 and 100 K. A near infrared cavity ring-down absorption spectrometer (CRDS) working on the v2 = 3 ← 0 transition of H3+ (λ = 1382 nm) has been used to monitor the H3+ (v = 0) ion number density in decaying afterglow plasma. The plasma was created in helium gas with small admixtures of argon and hydrogen by pulses of microwaves. The measurements were carried out for hydrogen number densities ranging from 1013 up to 1016 cm−3. The total pressure in the discharge tube was 4–10 mbar. The temperature of the recombining ions was determined from the Doppler broadening of absorption lines. The obtained effective recombination rate coefficients are α (H3+ (v = 0)) = (0.8 ± 0.3) × 10−7 cm3s−1 and α(H3+ (v = 0)) = (2.3 ± 1.1) × 10−7 cm3s−1 at 330 and 100 K, respectively. The influence of the formation of H5+ at higher pressures and lower temperature is also discussed.