In the present paper, a core–shell structured nanocomposite modified with rhodamine derivative was constructed for nitrite ion sensing, where its inner core and outer shell were composed of silica nanospheres and silica molecular sieve MCM-41, respectively. A rhodamine derivative was covalently grafted into MCM-41 tunnels. This nanocomposite was characterized and confirmed by IR spectra, electron microscopy images and thermogravimetric analysis. Then its sensing performance toward nitrite ion was evaluated from its UV–vis absorption and emission spectra. Limit of detection as low as 2μM and good selectivity were observed. Further analysis on probe emission decay dynamics suggested that this sensing procedure was accomplished through an adductive reaction between NO + and our probe.