Flow cytometry (FC) is a pivotal tool for studying the physical and chemical properties of particles. State-of-the-art FC systems are highly advanced, yet they are expensive, bulky, and require high sample volume, qualified operators, and periodic maintenance. The manipulation of particles suspended in viscoelastic fluids has received increasing attention, especially for miniaturized flow cytometry technologies. This study presents a miniaturized optical capillary FC device using the viscoelastic focusing technique. A straight, one inlet/outlet microcapillary device is precisely aligned to a fiber-coupled laser source and detectors. Forward scattered, side scattered, and fluorescently emitted light signals are collected and analyzed in a real-time environment. The developed platform fits onto an inverted microscope stage enabling real-time microscopy imaging of the particles of interest together with the flow cytometry analysis. We achieved stable viscoelastic focusing and performed FC measurements for rigid polystyrene beads (diameters: 2 - 15 μm), non-spherical human erythrocytes, and canonical shape metaphase human chromosomes. We performed cytometry measurements with a throughput of 100 events/s yielding a coefficient of variation of 2%. This newly developed FC device is a versatile tool and can be operated with any inverted microscope to get the mutual benefits of optical and imaging FC measurements. Furthermore, it is possible to extend these benefits by adding more back-end tools, such as optical trapping and Raman spectroscopy.