Single crystals of a metal organic complex (C5H12N)CuBr3 (C5H12N = piperidinium, pipH for short) have been synthesized, and the structure was determined by single-crystal X-ray diffraction. (pipH)CuBr3 crystallizes in the monoclinic group C2/c. Edging-sharing CuBr5 units link to form zigzag chains along the c axis, and the neighboring Cu(II) ions with spin-1/2 are bridged by bibromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner Fisher formula for the antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant J approximate to -17 K. At zero field, (pipH)CuBr3 shows three-dimensional (3D) order below T-N = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant J' = 0.91 K is obtained and the ordered magnetic moment m(0) is about 0.23 mu(B). This value of m(0) makes (pipH)CuBr3 a rare compound suitable to study the 1D-3D dimensional crossover problem in magnetism, since both 3D order and one-dimensional (1D) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field mu H-0 >= 3 T is applied along the a' axis. The mu H-0-T phase diagram of (pipH)CuBr3 is roughly constructed.