Ferroelectric barium-strontium-titanate (BST) varactors are becoming extremely important particularly for frequency-agile RF and microwave circuits. Tunable bandstop filters are desired to eliminate unwanted signals for several communication systems. In this paper, a compact tunable bandstop filter (BSF) based on a single hairpin resonator, using ferroelectric BST varactors, is also presented. The frequency response of proposed BSF can be adjusted by increasing or decreasing the length, width, and space for the coupled line hairpin resonator. One pair of variable capacitors has been incorporated to the filter for tuning and miniaturization purposes. The notch frequency of BSF can be tuned from 705 MHz to 1.035 GHz with a tuning voltage of 6 Volts utilizing BST varactors.