The use of diamond to develop electrochemical (EC) sensors opens up promising perspectives with interests for biosensing applications. However, in spite of the superior EC properties of diamond, two crucial issues remain to be solved: to improve (i) the electrode stability and (ii) the charge transfer rate k0. To address these issues, the influence of the boron concentration and of EC treatments on EC behaviour was assessed. Our results were compared with those obtained on a commercial diamond electrode. The reactivity of the as‐grown electrodes was very high whatever the boron concentration. However, a systematic linear increase of the charge transfer resistance (Rt) with time, highly dependent on the boron concentration, was observed. The most favourable EC behaviour was obtained for a boron concentration close to the phase separation limit and attributed to a higher effective doping. Moreover, a further EC‐treatment of the diamond samples considerably enhances the electrodes stability. Optimized samples, obtained after EC‐treatment, show a high reactivity (k0 = 0.2 cm/s) equivalent to that of platinum as well as a remarkably enhanced stability.