No. In terms of sex work, decriminalisation means it is not a criminal offence, i.e. not a crime. Legalisation mean also not a crime, but subject to restrictions and regulations.

In NSW (Aus) and New Zealand (both decriminalised), there are no laws restricting sex work. Local councils may have zoning laws restricting where brothels may operate, but sex work itself is fully legal.

What's the difference?

Crimes go through a criminal justice track, and outcomes may include jail time.

Illegal actions go through a civil justice track, and typically result in fines and/or some sort of civil restitution for victims.

If you ignore building codes you're acting illegally. If you ignore building codes and people die you're a criminal.

Which is fine as far as it goes. But criminality is often defined politically, not empirically in terms of outcomes.

Sex work is complicated precisely because it's on the edge of consensus morality. It has so much moral and political baggage, and for those who care it's so difficult to manage in ways that minimise harm for all involved, that it's almost the definition of a political football.

It doesn't help that authoritarians are invariably utterly hypocritical about it. Sex workers know that business is going to boom whenever a convention of self-styled moral hawks hits town.

So there's always political pressure to keep that hypocrisy hidden, which makes the criminal/civil line even more of a hot-button issue than it would be anyway.

Decriminalisation means relaxing the penalties so you get a civil fine, not a criminal charge. Jaywalking may get you a ticket, but it doesn't make you a criminal. Many people advocate for the decriminalisation of many drugs, including hard drugs; the idea is that even if we don't think heroine use is okay, locking someone up for using heroine isn't solving the problem.

Legalisation means making it actually legal, as many US states have now made marijuana, or as NZ has made sex work. It can still be regulated or taxed, but in general its fine.