MEPs ask the EU candidate country to follow EU sanctions on Moscow.
MEPs want Serbia to reconsider its position toward Russia.
Since the beginning of the Russian invasion of Ukraine, Belgrade has maintained close ties with Vladimir Putin's country despite the EU's stance.
On Wednesday, members of the European Parliament approved an annual assessment report regretting that Serbia has not aligned with EU sanctions on Russia. The text was adopted with 523 votes in favour, 78 against and 34 abstentions.
MEPs are asking the newly elected government -- following elections in April -- to "urgently align" with the EU's stance.
"I think there is real urgency here, particularly in the case of Serbia, to make some important domestic choices on this ground," said the MEP in charge of the report, Vladimir Bilcik, from the EPP.
"Because it is a country that has always looked in different directions when it comes to its foreign policy. But I think now it is time to decide where it stands. And I hope Serbia will make a clear decision in direction of Europe."
Since 2014, Serbia has been in negotiations with the EU to join the bloc. But its close relations with Russia could add a new obstacle to dialogue.
The differences have extended to several issues. The report also regrets the lack of progress and even backsliding in rule of law, media freedom, and the fight against corruption. But it is hopeful as the new Serbian parliament is more pluralistic.
And according to MEPs involved in the process, this is the time to deliver on reforms in order to make progress on joining the EU.
The agreements 'are being put into question'
The relationship of Serbia with neighbouring Kosovo is also one of the main issues in terms of it getting the green light to join the bloc.
Kosovo, a former province of Serbia until its declaration of independence in 2008, is a potential candidate to join the EU.
But Serbia, as well as five other countries in the EU, do not recognise Kosovo's independence.
MEPs also want both Serbia and Kosovo to work on normalising relations.
"Concerning [Kosovo's] relations with Serbia, we included the need to improve relations not only on the political level but furthermore we paid special attention to the level of citizens: supporting people to people contact, multilingualism and the social-economic integration of Kosovo Serbs," said MEP Viola von Cramon-Taubadel.
"The text of the report highlights the need to normalise relations with Serbia based on mutual recognition as a priority and as a precondition for EU accession of both countries. The Belgrade-Pristina dialogue has not been very high on the agenda.
"The agreements which have been reached in the past are being put into question, which shows a lack of serious engagement and that was criticised by many individual MEPs."
Kosovo's road to the EU visa-free regime
The European Parliament voted in favour of Kosovan citizens being granted the right to enter the EU's Schengen area without the need for a visa.
Kosovo has seen a rise in its political stability and a greater commitment to its European path in the recent years, a reason why the MEPs asked the European Council to "urgently" adopt a visa-free regime.
For von Cramon-Taubadel, EU countries are the ones to blame for the issue.
"The visa liberalisation is still blocked at the level of the European Council, not here in the Parliament, not in the Commission."
The Netherlands and France are blocking a decision that was expected in the last EU-Balkans Summit at the end of June in Brussels.
"We really tried our best to unblock the situation", said the MEP.