The non-relativistic self-gravitating gas in thermal equilibrium in the presence of a positive cosmological constant \Lambda ( dark energy ) is investigated .
The dark energy introduces a force pushing outward all particles with strength proportional to their distance to the center of mass .
We consider the statistical mechanics of the self-gravitating gas of N particles in a volume V at thermal equilibrium in the presence of \Lambda .
It is shown that the thermodynamic limit exists and is described by the mean field equations provided N, V \to \infty with N / V ^ { \frac { 1 } { 3 } } fixed and \Lambda V ^ { \frac { 2 } { 3 } } 
fixed .
That is , \Lambda \to 0 for N, V \to \infty .
The case of \Lambda fixed and N, V \to \infty is solved too .
We solve numerically the mean field equation for spherical symmetry obtaining an isothermal sphere for \Lambda > 0 .
The particle distribution turns to flatten compared with the \Lambda = 0 case .
Moreover , the particle density increases with the distance when the cosmological constant dominates .
There is a bordering case with uniform density .
The density contrast between the center and the boundary may be significatively reduced by the dark energy .
In addition , the critical point associated to the collapse ( Jeans ’ ) phase transition is pushed towards higher values of N / [ T V ^ { \frac { 1 } { 3 } } ] 
by the presence of \Lambda > 0 .
The nature and the behaviour near the critical points is not affected by the presence of \Lambda > 0 .