Triplet exciton accumulation and singlet-triplet annihilation (STA) are major issues, which makes continuous-wave (CW) operation difficult, in organic lasers. We synthesized an organic laser dye, 2,6-dicyano-1,1-diphenyl-λ5σ4-phosphinine (DCNP), having a small singlet-triplet energy gap. In DCNP-doped 4-4΄-bis[(N-carbazole)styryl] biphenyl (BSBCz) films, the triplets formed on DCNP are easily transferred to BSBCz, resulting in the suppressed STA and triplet accumulation. With this system, we demonstrated true-CW laser operation, with a low threshold and high photostability. Laser emission was further characterized by plane-polarized light output, far-field beam interference, exciton decay lifetime, and visible beam observed on an illuminance paper.