Thermoplastic polyurethane (PU) elastomers have attracted significant attention because of their many important industrial applications. However, the creation of fire-retardant and anti-dripping PU elastomers has remained a grant challenge due to the lack of crosslinking and weak interchain interactions. Herein, we report a mechanically robust, biodegradable, fire-retardant, and anti-dripping biobased PU elastomer with excellent biodegradability using an abietic acid-based compound as hard segments and polycaprolactone diol (PCL) as soft segments, followed by physically crosslinking with cellulose nanocrystals (CNC) through dynamic hydrogen-bonding. The resultant elastomer shows the balanced mechanical and fire-retardant properties, e.g., a tensile strength and break strain of 9.1 MPa and 560%, a self-extinguishing ability (V-0 rating in UL-94 testing), and an anti-dripping behavior. Moreover, the as-developed PU can be completely degraded in 1.0 wt.% lipase solution at 37 °C in 60 days, arising from the catalytic and wicking effect of CNC on PU chains. This work provides an innovative and versatile strategy for constructing robust, fire-retardant, anti-dripping, and biodegradable PU elastomers, which hold great promise for practical applications in electronic and automobile sectors.