Short answer: it depends on what features of C++ that you use - AND - whether you have enabled the compiler to use them.
Specific example to support above example: Exception Handling in C++: with the try, throw, catch statements. Some compilers have a command line option to enable or disable support for exception handling - i.e. code with try throw catch will compile. Enabling support for exception handling, even without using it, can cause the compiled binary to increase by up to a third in size compared to when it is switched off. So if memory for holding your program is scarce and you don't use exception handling or can find another way to report errors, then turn off this in the compiler.
Your question applies particularly for embedded real-time systems (e.g. consumer electronics, control systems) and semi-embedded (i.e. kiosks, mobile phones, game consoles) where resources (CPU time and RAM are not so abundant as on a desktop). However, I worked on 2 embedded real time projects where part of the software stack was written in C++, one was in optical drive firmware (DVD/CD burners) and the other was fibre-optic multiplexor control software.
I agree with @mootinator that it depends on who you are working with because it could impact the delivery of your project if your fellow team members need to get up to speed with C++.
C++ can bring benefits of reuse and maintainability via the Object Oriented Programming concepts that it provides.
So you might want to research carefully the performance (speed and memory) of C++ in your chosen field. Once you are confident that you can still use C++ following this research, you then need to implement and test regularly to confirm that the performance needs of your project are still being met, so that there are no surprises.