This paper presents an experimental and modelling study of NO formation in high pressure premixed flames. Experiments were performed in a high-pressure counterflow burner in which laminar premixed CH₄/air flames were stabilised at equivalence ratios of E.R = 0.7, 1 and 1.2 and for pressures varying from 0.1 to 0.7 MPa. We report quantitative NO mole fraction profiles measured by Laser Induced Fluorescence. The effects of pressure and equivalence ratio on NO formation are discussed. These results are compared to the simulations using two reaction mechanisms: NOmecha2.0 associated to a detailed mechanism for methane oxidation: GDFkin®3.0 and the mechanism from Klippenstein et al., which is the most recent high-pressure NOx formation mechanism available in the literature. In general, both mechanisms are able to predict NO correctly in lean and stoichiometric high pressure flames; however, in rich flames, GDFkin®3.0_NOmecha2.0 gives the best predictions. The performances of these mechanisms are also tested on NO measurements in high-pressure flames from the literature. A kinetic analysis is then presented to identify the main pathways that lead to the formation and consumption of NO and highlight the differences between the two mechanisms, as well as a sensitivity analysis to identify important reactions that influence the formation/consumption of NO in our high pressure flames.