Abstract In this paper, the authors study oscillatory and asymptotic behavior of solutions of a class of nonlinear third order neutral differential equations with positive and negative coefficients of the form (E) ( a ( t ) ( b ( t ) ( y ( t ) + p ( t ) y ( σ ( t ) ) ) ′ ) ′ ) ′ + q ( t ) G ( y ( α ( t ) ) ) − h ( t ) H ( y ( β ( t ) ) ) = 0 $$\begin{equation*}(a(t)(b(t)(y(t)+p(t)y(\sigma(t)))^{\prime})^{\prime})^{\prime} +q(t)G(y(\alpha(t)))-h(t)H(y(\beta(t)))=0 \tag{E}\end{equation*}$$ for 0 ⩽ p(t) ⩽ p 1 <1 and −1 < p 2 ⩽ p(t) ⩽ 0. The results in this paper generalize the results of [LI, T.—ZHANG, C.—XING, G.: Oscillation of third-order neutral delay differential equations, Abstr. Appl. Anal. 2012 (2012), Article ID 569201] and various results in the literature. We establish new conditions which guarantees that every solutions of (E) either oscillatory or converges to zero. Examples are considered to illustrate the main results.