The most recent terrorist attacks in April of 2019 led to governments advising against travel to Sri Lanka. The warning has been lifted since, but visitors to Sri Lanka are asked to be vigilant, especially in crowded areas.
Until these terrorist attacks, Sri Lanka was a remarkably safe place to travel in, and violent crime against foreigners was virtually unheard of. This is still a place where, despite 25 years of brutal civil war, the theft of two bicycles can be considered a crime wave.
Petty theft is less common than in many other parts of Asia (and rarer than in most European and American cities), though you should still take sensible care of your belongings. Pickpockets sometimes work in crowded areas, while thefts from hotel rooms are occasionally reported. Many hotels and guesthouses ask guests to deposit valuables in their safe, and it’s sensible to do so when you can.
In addition, make sure you keep a separate record of all your bank card details (along with the phone numbers needed in case of their loss) and passport information. It’s worth taking a photocopy of the pages from your passport that contain your personal details.
Muggings are very rare, though single travellers (especially women) should avoid dark beaches late at night – Negombo and Hikkaduwa have particularly bad reputations.
If you do experience crime in Sri Lanka, report it to the police. If you have anything stolen, there’s little chance the police will be able to recover it for you, but you’ll need a report for your insurance claim. Given the fact that you might not find any English-speaking policemen on duty (even at so-called “tourist police” stations), you might try to get someone from your guesthouse to come along as an interpreter. The process of reporting a crime is usually a laborious affair, with much checking of papers and filling in of forms.