We analyze the erythrocyte aggregation by the biospeckle laser phenomenon and calculate characteristic parameters to develop non-invasive hemorheological techniques. Biospeckle is more complex than other light-based techniques, such as light transmission, providing information about the dynamics of the scatterers, their size, and morphology. Dextran 500 kDa combined with plasma and phosphate-buffered saline was used to induce controlled in vitro erythrocyte aggregation. Red blood cell aggregation was studied using an objective speckle setup in a microchip sample chamber. The speckle grain sizes were determined, and parameters to characterize the morphology of the erythrocyte aggregates were proposed. The inertia moment and the correlation coefficient were determined to assess the cells aggregation dynamics.