Via Copenhagen: Copenhagen can be reached amongst others from Hamburg (Germany) by bi-hourly EC trains. Direct regional Öresundstrains (https://www.oresundstag.se) from Copenhagen Central Station to Karlshamn as follows:

• During the week: Hourly from 04:44–20:44
• On Saturdays: Hourly from 05:44–20:44
• On Sundays: Hourly from 06:44–20:44
• Regular travel time: ~2¾ h

Ticket sales:

• On https://www.oresundstag.se
• Via the Blekingetrafiken-app (might lead to a cheaper option)
• Via your travel agency
• Via vending machines (Tip: look out for the red vending machines (“Skånetrafiken” or “Blekingetrafiken”, not the ones from the Danish operator “DSB”)).

Prices:

• Second class: ~30 €
• First class: ~35 €

Hints:

• Especially during rush hours, it is advisable to invest in a first-class ticket in order to get a seat and have space for yourself and your luggage (marginal surcharge of ~5 €).
• Usually, the last three coaches of the train take all the way to Blekinge, while the first three coaches are uncoupled in Kristianstad along the way. The destination is usually displayed above the doors; you should sit in the train part with destination “Karlskrona”. If in doubt, please feel free to ask the conductor.
• Be prepared for a passport check at the first station in Sweden upon passing the bridge (Hyllie).

From Stockholm:
Long-distance trains by two operators with compulsory reservations and one switch in Hässleholm or Alvesta.

• SJ: https://www.sj.se/en
  • Daytime departures: Apprx. hourly between 05:21 and 17:21.
    Switch in Hässleholm*
    Regular travel time: ~6 h
  • Alternative departure: Night train 23:10 with coach (seats), couchette (bunk beds) and sleeper (real beds).
    Switch in Hässleholm* 05:01.
• Snälltåget: https://www.snalltaget.se/en
  • Daytime departures: 09:33 and 16:20.
    Switch in Alvesta to connecting bus (included in the ticket).
    Regular travel time: ~5¼ h
  • Alternative departures: 12:20 and 23:10 (night train).
    Switch in Hässleholm* 06:05.

* Hässleholm – Karlshamn: typically by Öresundstrain (https://www.oresundstag.se) or local train (“Pågatåg”, https://www.skanetrafiken.se/sok-resa/, Swedish only), each once per hour except during nighttime.

Hints:

• Please observe that railroad works have been announced for the week-end of 15-16/06, which might affect the schedule and the availability of tickets.
• When coming by night train from the north, switching trains later in Malmö or Lund allows for longer sleeping time at a slightly higher cost .
• Long-distance tickets usually include the regional Öresundstrains, but not necessarily the local trains. The valid connection is specified on your ticket.

From Berlin and Hamburg:
Long-distance trains by two operators with compulsory reservations and one switch, typically in Hässleholm.

• SJ: https://www.sj.se/en offers an almost daily service (train EN 346) with coach (seats), couchette (bunk beds) and sleeper (real beds).
  • Departures: Berlin Gesundbrunnen 18:37, Hamburg Hbf 22:03
  • Switch in Hässleholm* 05:10
• Snälltåget: https://www.snalltaget.se/en offers an almost daily service with coach and couchette (but no sleeper). As-early-as-possible booking is recommended.
  • Departures: Berlin ~21:00 (time and departure station subject to change), Hamburg Hbf: 23:59
  • Switch in Hässleholm* 09:05

* Hässleholm – Karlshamn: by Öresundstrain (https://www.oresundstag.se) or local train (“Pågatåg”, https://www.skanetrafiken.se/sok-resa/, Swedish only), once per hour except during nighttime.

Hints:

• Please observe that railroad works have been announced for the week-end of 15-16/06, which might affect the schedule and the availability of tickets.
• The night trains between Germany and Sweden are highly popular. As-early-as-possible booking (once the tickets become available) is recommended.
• Long-distance tickets usually include the regional Öresundstrains, but not necessarily the local trains.