We consider a deformed fifth-order Korteweg–de Vries (D5oKdV) equation and investigated its integrability and group theoretical aspects. By extending the well-known Lax pair technique, we show that the D5oKdV equation admits a Lax representation provided that the deformed function satisfies certain differential constraint. It is observed that the D5oKdV equation admits the same differential constraint (on the deforming function) as that of the deformed Korteweg–de Vries (DKdV) equation. Using the Lax representation, we show that the D5oKdV equation admits infinitely many conservation laws, which guarantee its integrability. Finally, we apply the Lie symmetry analysis to the D5oKdV equation and derive its Lie point symmetries, the associated similarity reductions and the exact solutions.