This paper proposes a low-power multi-mode injection-locked transmitter (TX). A negative-transconductance active-inductor-based oscillator for the multi-mode modulations (e.g., ASK/FSK/BPSK) is designed to cover wide frequency bands, e.g., 400 MHz, 800 MHz, and 915 MHz. By making use of the injection locking technique, the phase noise of the active-inductor-based oscillator is lowered to the level that is close to the 'clean' incident signal. To reduce the power consumption while providing operating flexibility, the TX is digitally controlled to switch the ASK/FSK/BPSK modulations. The proposed TX is fabricated in a 65-nm CMOS technology with a nominal supply voltage of 1 V. The measurement results show the TX prototype achieves the maximum data rate of 1 Mb/s with an output power of -12dBm under a 2-mW power consumption.