The characteristics of oxygen dissolution accelerated by the use of micro-bubbles in a viscoelastic fluid were studied. An aqueous solution of a combination of a cationic surfactant and of a counter-ion supplier was used as a viscoelastic fluid. Flow visualizations and measurements on the time variation of the oxygen concentration were performed. From the results, it was found that the dissolution of oxygen rapidly occurs by the use of microbubbles, but the dissolution becomes slow in a highly elastic fluid. The flow observation of bubbles in a highly elastic fluid showed a chaining effect with bubble ascension. Bubble chaining was found to accelerate the agglomeration of bubbles and decrease the apparent gas-liquid interface area. Thus, such a chaining effect was concluded to disturb the dissolution of oxygen.