To increase reception in Long Term Evolution (LTE) network inside a building, a repeater is needed. The antenna used in the repeater inside the building is usually a high gain antenna with omnidirectional radiation pattern. Meanwhile, to increase data rate in LTE, one of methods used is by using Multiple Input Multiple Output (MIMO) antenna. In this paper, the omnidirectional MIMO antenna at 1.8 GHz for LTE applications has been designed and realised. The single element of this MIMO antenna is a collinear microstrip antenna array. The design and simulation were done using 3D electromagnetic simulator software, while antenna realisation was done using FR4 microstrip with a thickness of 1.6 mm and permittivity of 4.4. The measurement results showed that this antenna has 359 MHz bandwidth in frequency range at 1.6-1.9 GHz, with a return loss less than -10 dB. The antenna gain is around 7.4 to 8.7 dBi with omnidirectional radiation pattern and mutual coupling is around -22 dB to -27 dB.