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We investigate carrier and collective mode dynamics in 2H-NbSe₂ using time-resolved optical pump-probe spectroscopy and compare the results with first-principle calculations. Broadband ultrafast reflectivity studies of 2H-NbSe₂ in a wide temperature interval covering the normal, charge density wave (CDW) and superconducting phase were performed. Spectral features observed in the transient reflectivity experiment were associated with specific optical transitions obtained from band structure calculations. Displacive excitation of coherent phonons show CDW-associated coherent oscillations of the soft phonon mode across the whole spectral range. Temperature evolution of this coherent phonon mode in the low-excitation linear regime shows softening of the mode down to the T_CDW with subsequent hardening below T_CDW. From first principle calculations of electron-phonon coupling we associate the few picosecond electron-phonon relaxation time τ₂ with a specific group of phonons with frequencies around 20 meV. On the other hand, the anomalously long relaxation time of τ₃~100 ps is associated with anharmonicity-driven phonon-phonon scattering. All time dependent relaxation processes result from anomalies near the second order CDW phase transition.