This work presents a K _α-band thin-film compact differential analog phase-shifter implemented in a custom graphene monolithic microwave integrated circuit (MMIC) technology. The design exploits a distributed-type configuration utilizing graphene diodes as shunt tuning loads. The prototype is realized on an 8.1 µm-thick flexible polyimide (PI) substrate, and its core occupies less than 0.18 mm ² of chip area. The evaluation of the fabricated circuit reveals an average S ₂₁ measurement of −3.2 dB in the frequency band of 20–30 GHz with a tunable phase difference (∆Φ) exceeding 90°. The introduced thin-film phase shifter promotes the realization of compact flexible and cost-effective solutions for next-generation high-frequency systems.