Goalkeeper Sergio Romero was in particularly inspired form as Delio Rossi's men claimed another valuable point in their mission to book a second season in Serie A, with Samp spurning several chances to win through young striker Mauro Icardi.
Napoli's forward line suffered from a rare lack of cutting edge and ended the day four points behind Juve, who were surprised by a 1-0 defeat to Roma on Saturday night.
Sampdoria were given the confidence to dominate the first half by the heroics of Romero.
The Argentinian stood tall to clear a dangerous Giandomenico Mesto cross before taking no chances as he punched away a fierce strike from Lorenzo Insigne.
Samp had bared their teeth in between times, Gianluca Sansone looking lively when put through by Icardi, but Morgan De Sanctis was there to smother the ball.
Edinson Cavani got in the way of a Marek Hamsik effort but could not add zip to the follow-up and Romero parried, with the Samp keeper then leaping on to a close-range shot from Insigne.
Romero had weathered the storm and now it was the turn of De Sanctis to keep a dynamic Samp outfit at bay.
Lorenzo De Silvestri and Andrea Poli could not beat the Italy international, but his blushes were spared when Valon Behrami cleared an Andrea Costa header off the line.
Icardi's follow-up drew a fine save from De Sanctis and Napoli raced up the other end, Insigne providing a finish to forget when Hamsik chested the ball through the back-line.
De Sanctis denied Samp the half-time lead they deserved, though, as he pounced low to his left to deny a quick Sansone raid.
As play resumed Behrami made a dedicated block on Icardi, who had escaped the attentions of marker Miguel Britos.
Icardi beat his man again in the 54th minute, but his effort from 30 yards was too ambitious, with Romero soon called back into action to palm away a swerving effort from Insigne.
Samp could sense their opportunity and Icardi was unlucky not to connect better with a sweet cross from Eder.
Another spell of home pressure followed and Romero had to snaffle a Hugo Campagnaro header before repelling a trademark screamer from Hamsik.
The last five minutes would belong to Napoli but, try as they might, Walter Mazzarri's men could just not force home a winner.
Substitute Goran Pandev might have been the hero had he connected with a loose ball in the Samp box but Romero snaffled it up to ensure a frustrating day for Napoli.