District Judge Lucy Koh in San Jose, California, rejected the companies' bid to dismiss claims.
Koh said the existence of "Do Not Cold Call" agreements among various defendants "supports the plausible inference that the agreements were negotiated, reached, and policed at the highest levels" of the companies.
She said that the fact that six identical agreements were reached in secrecy among seven defendants in a span of two years suggests that these agreements resulted from collusion.
On the plus side, Koh dismissed a claim brought under California's unfair competition law.
The class-action lawsuit was brought by five software engineers who accused the companies of conspiring to limit pay and job mobility by eliminating competition for labour, costing workers hundreds of millions of dollars.
In 2010, the Department of Justice settled antitrust probes against the companies. Without admitting wrongdoing, the tech companies agreed not to take steps to restrict competition for workers.
The court has seen an email trail involving Steve Jobs and Eric Schmidt. Jobs was furious that Schmidt had broken the agreement by poaching one of Apple's staff.
Jobs demanded that Schmidt fire the engineer and tell off his recruiting department. Apparently Schmidt did this. Google's staffing director said the employee who recruited the engineer would be fired, and added: "Please extend my apologies as appropriate to Steve Jobs."