Different pulse Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR) techniques are used to study the electronic and geometric structure of (tetraphenylporphyrinato)cobaltate(II) with pyridine as an axial ligand (cobaltous tetraphenylporphyrin(pyridine), CoTPP(py)). This complex is considered as a model for the heme group in deoxygenated hemoglobin and myoglobin. For the first time, the small hyperfine and nuclear quadrupole interactions of the porphyrin nitrogens of CoTPP(py) are determined using three-pulse electron spin-echo envelope modulation (ESEEM), hyperfine sublevel correlation (HYSCORE), and double nuclear coherence transfer (DONUT)-HYSCORE spectroscopy as well as Davies-ENDOR, and hyperfine correlated ENDOR (HYEND). The assignment of the different cross-peaks in the HYSCORE spectra is shown to be considerably facilitated by the DONUT-HYSCORE experiment. Furthermore, the hyperfine interactions of the surrounding protons are investigated by Davies- and Mims-ENDOR and HYSCORE spectroscopy at X- and S-band microwave frequencies, For the first time, the potential of proton HYSCORE spectroscopy at S-band is demonstrated. Assignment of the observed couplings is facilitated using deuterated pyridine as the axial ligand. The interactions with the ortho and meta protons of pyridine and with the protons of the porphyrin ligand are determined. From the Davies-ENDOR spectra of CoTPP(py) and CoTPP([N-15]py), the hyperfine and nuclear quadrupole couplings of the pyridine nitrogen are evaluated. From the hyperfine and nuclear quadrupole parameters, structural (internuclear distances) and electronic information is derived. Comparisons are made with known EPR and ENDOR studies on a number of porphyrin systems with different metal ions. The similarities and differences are discussed in detail.