This paper presents a novel tri-band high- temperature superconducting bandpass filter based on the tri-mode resonance of an embedded stub-loaded resonator (ESLR). This ESLR is analyzed using the even- and odd-mode method, demonstrating the emergence of three resonant frequencies and two transmission zeros in the ESLR circuit. The coupling structure, using capacitively loaded parallel coupled lines, is studied to realize the equal coupling coefficients at three resonant frequencies. Two tapped lines are used to achieve the desired external coupling under prior specifications. The lossless lumped-element equivalent circuits for three passbands are proposed. Finally, a third-order tri-band filter with the 4% fractional bandwidth is designed and fabricated with three passbands centered at 1.8, 2.4, and 3.5 GHz, respectively, corresponding to the GSM, WLAN, and WiMAX communication applications. The measured results agree well with simulated ones, showing very low in-band insertion loss, i.e., 0.07, 0.08, and 0.11 dB, in the three passbands, respectively.