The demonstration at the gates of parliament in Warsaw was called by the KOD pro-democracy movement, which is critical of the ruling Law and Justice (PiS) party's policies on media, education and the Constitutional Court.
The restrictions planned by the conservative party grant access to the parliament's press gallery to only two journalists per outlet, and ban them from shooting still pictures or video.
The limits prevent the media from recording images of lawmakers when they break the rules, for example by voting for an absent colleague.
The only video images available will be provided by the parliament's official video service.
The new system forces journalists to work at a media centre located in another building, limiting their access to lawmakers.
Inside the parliament opposition lawmakers chanted "Democracy!" and "Free media!".
The speaker of parliament had to interrupt the session and hours later transferred the proceedings to another gallery so lawmakers could vote on the state budget for 2017.
The quorum for the vote was met, though the opposition slammed it as illegal.
PiS leader Jaroslaw Kaczynski condemned the protesting lawmakers' actions as "parliamentary hooliganism".
In an earlier act of protest by journalists, more than 20 Polish media outlets refused to cover parliament on Friday.
Those joining the media boycott included major dailies Gazeta Wyborcza and Rzeczpospolita, as well as two large private radio channels.
Late Friday evening, protesters were still arriving at the entrance to parliament to join the other demonstrators.
The PiS has defended the measure, saying it seeks to ensure a comfortable work environment for both lawmakers and journalists.
"It's definitely not meant to reduce transparency," said PiS lawmaker Arkadiusz Mularczyk.
Several dozen journalists had rallied outside the parliament building on Thursday.
In a letter, they asked the speakers of both parliamentary chambers to drop the planned policy.
"It will only allow politicians to steer clear of journalists easily," the letter says.