Neural　electrode　interfaces　are　essential　to　the　stimulation　safety　and　recording　quality　of　various　bioelectronic　therapies.　The　recently　proposed　hierarchical　platinum-iridium　(Pt-Ir)　electrodes　produced　by　femtosecond　lasers　have　exhibited　superior　electrochemical　performance　in　vitro,　but　their　in　vivo　performance　is　still　unclear.　In　this　study,　we　explored　the　electrochemical　performance,　biological　response,　and　tissue　adhesion　of　hierarchical　Pt-Ir　electrodes　by　implantation　in　adult　rat　brains　for　1,　8,　and　16　weeks.　Regular　smooth　Pt-Ir　electrodes　were　used　as　a　control.　The　results　showed　that　the　electrochemical　performance　of　both　electrodes　decreased　and　leveled　off　during　implantation.　However,　after　16　weeks,　the　charge　storage　capacity　of　hierarchical　electrodes　stabilized　at　~16.8　mC/cm2,　which　was　15　times　that　of　the　smooth　control　electrodes　(1.1　mC/cm2).　Moreover,　the　highly　structured　electrodes　had　lower　impedance　amplitude　and　cutoff　frequency　values.　The　similar　histological　response　to　smooth　electrodes　indicated　good　biocompatibility　of　the　hierarchically　structured　Pt-Ir　electrodes.　Given　their　superior　in　vivo　performance,　the　femtosecond　laser-treated　Pt-Ir　electrode　showed　great　potential　for　neuromodulation　applications.　[Figure　not　available:　see　fulltext.]　©　2022,　The　Author(s).