We present a unique laser sintering setup that allows real time studies of the structural evolution during laser sintering of polymer particles. The device incorporates the main features of classical selective laser sintering machines for 3D printing of polymers and at the same time allows in situ visualization of the sintering dynamics with optical microscopy as well as X-ray scattering. A main feature of the setup is the fact that it provides local access to one particle-particle bridge during sintering. In addition, due to the small scale of the device and the specific laser arrangement process, parameters such as the temperature, laser energy, laser pulse duration, and spot size can be precisely controlled. The sample chamber provides heating up to 360 °C, which allows for sintering of commodity as well as high performance polymers. The latter parameters are controlled by the use of a visible light laser combined with an acousto-optic modulator for pulsing, which allows small and precise spot sizes and pulse times and pulse energies as low as 500 μs and 17 μJ. The macrostructural evolution of the particle bridge during sintering is followed via optical imaging at high speed and resolution. Placing the setup in high flux synchrotron radiation with a fast detector simultaneously allows in situ time-resolved X-ray characterizations. To demonstrate the capabilities of the device, we studied the laser sintering of two spherical PA12 particles. The setup provides crucial real-time information concerning the sintering dynamics as well as crystallization kinetics, which was not accessible up to now.