Nanocomposite of metal oxide semiconductors are multifunctional and one such nanocomposite ZnO/ Mn<sub>3</sub>O<sub>4</sub> (2:1) was synthesized ZMA4 (ZnO: Mn<sub>3</sub>O<sub>4</sub> using ammonia), ZMH4 (ZnO: Mn<sub>3</sub>O<sub>4 </sub>using hexamine) by the coprecipitation route. In addition pure ZnO was prepared using ammonia (ZA) and hexamine (ZH). XRD reveals the crystal structure of ZnO/Mn<sub>3</sub>O<sub>4</sub> and the average crystallite size is estimated as 43, 12, 42 and 18 nm for ZA, ZMA4, ZH and ZMH4 respectively. FTIR bands at 440-490 and 616-621cm<sup>-1</sup> are due to Zn-O and Mn-O vibrational bands. Presence of manganese in nanocomposites is confirmed by EDS. SEM micrographs indicate the formation of nanoparticles (ZA and ZMA4) and nanorods (ZH-98 nm length, 63 nm dia). Excitonic absorption peaks at 370 and 290 nm in the UV-Vis spectra are attributed to ZnO/Mn<sub>3</sub>O<sub>4</sub> nanocomposite. The bandgap is estimated as 2.7, 2.3, 2.6 and 3.0 eV for ZA, ZMA4, ZH and ZMH4 respectively. FL spectra of ZA, ZMA4 expose the emission at 366 and 396 nm owing to the near band edge (NBE) and zinc interstitial at 468 nm. ZH nanorods show the emission at 386, 468 and 558 nm which are attributed to NBE, zinc interstitial and oxygen vacancy respectively. The reduction of oxygen vacancy is observed in ZMH4 as manganese effectively changes the morphology from nanorod to nanoparticle. The second harmonic generation efficiency measured for ZA and ZH is 0.6 and 0.9 times KDP using Q - switched Nd: YAG laser (1064nm, 10 Hz, 9 ns).