Cooperative upconversion luminescence (CUCL) occurs in spectral regions in which single ions do not have energy levels. However, all results reported so far are concentrated on luminescence properties from Yb3+ ions-doped various hosts. Here, we report the observation of nonlinear negative transmittance (NNT) at continuous-wavelength (CW) 980-nm laser diodes (LDs) pumping in silicate oxyfluoride glass ceramics (GCs)-containing CaF2:Yb3+ nanocrystals. The unique optical nonlinearity is analyzed based on energy-level transitions, dynamic evolution, rate equation, and power transmission equation, which can be explained as the cooperative optical absorption for the intense CUCL of Yb3+ ions. The NNT in the CaF2:Yb3+ nanocrystals-embedded GCs can be tailored with the power of a CW 980-nm LDs, which possesses potential for the development of future optical limiters and switches.