The stability of coupled Langmuir and ion‐acoustic solitons has been investigated by means of numerical computations. Using the Zakharov equation to describe the envelope of the oscillating electric field, and the Korteweg–de Vries equation with the ponderomotive driving term, to describe the low‐frequency electron density variation, it was found that (1) Langmuir waves and short scale sound waves do not affect the soliton; (2) two solitons destroy each other when colliding; and (3) a long scale sound wave or ion‐acoustic soliton break up a coupled soliton in the interaction. Moreover, no initial condition far from a soliton state was found which would create a coupled soliton.