The accelerator instrumentation played a vital role in commissioning the ALS injector accelerator. It helped us to see whether electron dynamics agreed with our theoretical predictions and important beam parameters met the design specifications. It helped us to see where beam losses occurred and why. In this paper we will start with a brief description of the ALS accelerator complex and the expected performance of it. Then we will describe each diagnostics instrument by its construction, operational principle, requirements, and our experiences with it. We will descrive the wall current monitor, the scintillator, the Faraday cup, the beam collimator, the beam position monitor, the direct‐current current transformer (DCCT), the traveling wave electrodes (TWE), the Sabersky finger, and other special instruments. Finally, we will go into some detail on how we measured the beam emittances, the closed orbit, and the betatron tunes.