In this paper, existence of solutions of third-order differential equation $$y'''(t)=f(t,y(t),y'(t),y''(t))$$ with nonlinear three-point boundary condition $$\left\{ \begin{array}{l} g(y(a),y'(a),y''(a))=0,\\h(y(b),y'(b))=0,\\I(y(c),y'(c),y''(c))=0\end{array}\right.$$is obtained by embedding Leray-Schauder degree theory in upper and lower solutions method, where $a, b, c\in R, a |