Arrowroot (Maranta arundinacea L.) is a non-conventional food plant (NCFP) from Marantaceas species. Although this crop presents high nutritional, functional, and technological potential, its use has been neglected. To overcome this, studies on the NCFP exploitation by food producers have been recently intensified, mainly those applied in dairy products, since these products presented a great increase on their demand in the last decades. The aim of this work was to evaluate the effect of arrowroot flour contents (0, 1.5, 3.0, 4.0%, wt/wt) on the rheological properties, size distribution and optical microscopy in vanilla dairy dessert. The addition of flour showed a non-Newtonian shear-thinning flow behavior, by observing shear stress variation with shear rate, suggesting pseudoplastic behavior (n < 1). However, control samples had a complex modulus (G*) and loss angle tangent (tan δ) lower than the flour-added samples, suggesting that the flour addition increases the dessert’s hardness. Regarding size distribution, increased D[4,3] values were seen in the samples with flour added compared the control dessert (ranging from 12 to 50 µm and 5 µm, respectively, P > 0.05). Optical microscopy confirmed the impact of the addition of flour on the diameter increase in all the samples as the addition of increased flour content samples (4% wt/wt) resulted in great agglomeration of starch granules. Overall, the arrowroot flour addition improved technological properties of vanilla dairy desserts.