Ultrasonic flow meter transducer assembly. At least one some of the illustrative embodiment are systems including: a spool piece that defines an exterior surface, a central passage, and a transducer port extending from the exterior surface to the central passage; and a transducer assembly coupled to the transducer port. The transducer assembly includes: a transition element coupled to the spool piece, the transition element having a first end disposed within the transducer port, and a second end residing outside the exterior surface; a piezoelectric module with a piezoelectric element, the piezoelectric module directly coupled to the first end of the transition element and the piezoelectric module disposed within the exterior surface; a transformer module with a transformer disposed therein, the transformer module directly coupled to the second end of the transition element and the transformer module disposed outside the exterior surface; and an electrical conductor disposed within a passage through the transition element, the electrical conductor couples the transformer to the piezoelectric element.