The structural, magnetic, and transport properties of double perovskites Ba2MnRuO6 (BMRO) and LaBaMnRuO6 (LBMRO) have been investigated. Rietveld analysis of powder x-ray diffraction data show that BMRO adopts 9R rhombohedral structure with space group R3̄m while the partial doping of Ba by La leads the structure to orthorhombic with Pbnm space group. Structural as well as magnetic studies revealed that Ru ions are tetravalent in both compounds. The superexchange interactions between Mn 3+ (t2g3 eg1)-O-Ru 4+ (t2g4) lead to a ferromagnetic ordering in LBMRO. The direct metal-metal interactions are to be invoked to understand the weak magnetic nature of BMRO. Transport studies reveal that both samples have insulating behavior with variable range hopping type of conduction. Magnetoresistance (MR) measurements show a positive magnetoresistance (∼ 5 % for 1 T) in BMRO, which is not significantly varying within the temperature range measured while LBMRO exhibit a negative magneto resistance (∼ 25% for 1 T at 80 K), which increases while decreasing the temperature. © 2007 IEEE.