Making the design of efficient novel crystallizers a topic of growing interest in both academia and the pharmaceutical industry. One such innovation is the Coiled Flow Inverter (CFI), a helically coiled tube with alternating 90 ̊ bends, which has recently been introduced as a continuous crystallizer. The CFI enhances radial mixing, leading to plug flow behavior. This study focuses on the isothermal continuous antisolvent crystallization of pyrazinamide from its acetone solution using cyclohexane as an antisolvent in a CFI device, aiming to produce the metastable δ-polymorph of pyrazinamide, which exhibits a more desirable morphology than the stable α-polymorph. The effects of CFI geometry, initial supersaturation, residence time, and ultrasonic amplitude are examined in detail. All experiments resulted in the formation of the δ -polymorph, with no detectable α-polymorph. As the number of flow inversions in the CFI device increased, the crystal size distribution became narrower, with a smaller mean size. The crystallization yield, productivity, and crystal size distribution were found to be influenced by the careful selection of initial supersaturation, crystallizer length, and API solution-antisolvent flow rate. The application of ultrasound proved effective in preventing clogging and producing crystals with a narrow size distribution and small mean size. Lastly, a two-dimensional population balance model was developed for the steady-state antisolvent crystallization of pyrazinamide in the CFI, and the model demonstrated good agreement with the experimental results.