[en] The paper presents an empirical pointwise potential energy curve (PEC) of the extensively perturbed B(1)¹Π state of the KCs molecule constructed by applying an Inverted Perturbation Approach routine. The experimental term values in the energy range E(v′,J′)∈[14071;15502]cm⁻¹ involved in the fit were based on Fourier-Transform spectroscopy data obtained with 0.01 cm⁻¹ accuracy from laser-induced B(1)¹Π→X¹Σ⁺ fluorescence spectra in the present work (654 term values) combined with 520 term values from Birzniece et al. (2012) . The data set included vibrational v′∈[0,35] and rotational J′∈[7,233] quantum numbers covering about 85% of the potential well. The present fit reproduces the data included in the fit with a standard deviation 0.94 cm⁻¹. The empirical PEC contains an inflection at about R=4.1 Å that reflects the avoided crossing of two Ω=1 states corresponding to B(1)¹Π and c(2)³Σ⁺ states as predicted by ab initio calculations. - Highlights: • An empirical potential for first singlet Pi state of the KCs molecule was constructed. • Fourier-Transform spectroscopy yielded term values with 0.01 cm⁻¹ accuracy. • Data set included vibrational levels up to v = 35 covering 85% of the potential well. • The potential reproduces the fitted data with a standard deviation 0.94 cm⁻¹. • The empirical potential contains an inflection that reflects the avoided crossing