British armed forces are to take part in "three additional operations" aimed at supporting Nato allies, it said.
Defence Secretary Philip Hammond added recent unrest in Ukraine had caused "great concern" and it was right to provide "reassurance" to partners in Eastern Europe.
The annual operations are US-led.
HMS Montrose, a Type 23 frigate, will take part in a two-week long security exercise which will begin on Monday.
Exercise Baltops, the largest multinational maritime exercise in the Baltic Sea this year, will test the maritime capabilities among Baltic sea countries and allied nations.
More than 100 British soldiers will also take part in live-fire training in Estonia and Latvia as part of exercise Sabre Strike, which began on Sunday.
They join personnel from the US, Denmark, Estonia, Finland, Lithuania, Latvia and Norway.
Mr Hammond said: "The situation in Ukraine continues to be of great concern to the international community and it is right that Nato members and partners publicly demonstrate our commitment to the collective security of our Nato allies.
"The UK continues to play a central role in providing reassurance to our allies in Eastern Europe and the Baltic states.
"Our contribution to these exercises builds on other action we have taken, including the deployment of RAF Typhoons to the Nato air policing mission in the Baltic states."
Meanwhile, around 200 British infantry troops will take part in a live fire exercise in Poland in September, along with up to 7,000 personnel from the US and Canada.
It follows action already taken by the UK to reassure Nato's Eastern European members, the MoD said.
In April, four RAF Typhoons helped to carry out Nato's air policing role of the Baltic states of Estonia, Latvia and Lithuania as part of a long-standing rotation.
And in May, British soldiers from the 1st Battalion The Duke of Lancaster's Regiment joined 6,000 troops from Nato states in Estonia for a training exercise.
A bloody insurgency has gripped Ukraine's eastern provinces since Russia annexed the Ukrainian territory of Crimea in March - which followed a controversial referendum on joining Russia.
A Royal Navy warship has been sent to the Baltic Sea to join multinational military exercises in the region, the Ministry of Defence has said.