The conditions that come with this rule, from its official sources.
Conditions from official sources
Can get an eVisa instead when living in the EU, the US, Australia, Canada, the UK, Japan, Norway, New Zealand, the UAE or Switzerland with a residence permit valid for at least 180 days.
Can get an eVisa instead when holding a multiple-entry, non-electronic Schengen, US, Australian, UK, Irish, Japanese, Canadian, Norwegian or New Zealand visa valid for at least 90 days.
Passport validity
The source states no minimum passport validity.
Tourist entry only
These rules cover tourist visits. Work, study and transit follow other rules.
Visa-free nearby
Other places Sierra Leone passport holders can visit without a visa, within 2,500 km of Laayoune, nearest first.
SenegalDakar, about 1,450 km from LaayouneVisa-free · 90 days
GambiaBanjul, about 1,560 km from LaayouneVisa-free · 90 days